// file      : doc/manual.cli
// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

"\name=build2-package-manager-manual"
"\subject=package manager"
"\title=Package Manager"

// NOTES
//
// - Maximum <pre> line is 70 characters.
//

"
\h0#preface|Preface|

This document describes \c{bpkg}, the \c{build2} package dependency
manager. For the package manager command line interface refer to the
\l{bpkg(1)} man pages.

\h1#package-name|Package Name|

The \c{bpkg} package name can contain ASCII alphabetic characters
(\c{[a-zA-Z]}), digits (\c{[0-9]}), underscores (\c{_}), plus/minus (\c{+-}),
and dots/periods (\c{\c{.}}). The name must be at least two characters long
with the following additional restrictions:

\ol|

\li|It must start with an alphabetic character.|

\li|It must end with an alphabetic, digit, or plus character.|

\li|It must not be any of the following illegal names:

\
build
con prn aux nul
com1 com2 com3 com4 com5 com6 com7 com8 com9
lpt1 lpt2 lpt3 lpt4 lpt5 lpt6 lpt7 lpt8 lpt9
\

||

The use of the plus (\c{+}) character in package names is discouraged.
\N{Pluses are used in URL encoding which makes specifying packages that
contain pluses in URLs cumbersome.}

The use of the dot (\c{.}) character in package names is discouraged except
for distinguishing the implementations of the same functionality for different
languages. \N{For example, \c{libfoo} and \c{libfoo.bash}.}

Package name comparison is case-insensitive but the original case must be
preserved for display, in file names, etc. \N{The reason for case-insensitive
comparison is Windows file names.}

If the package is a library then it is strongly recommended that you start its
package name with the \c{lib} prefix, for example, \c{libfoo}. Some package
repositories may make this a requirement as part of their submission policy.

If a package (normally a library) supports usage of multiple major versions
in the same project, then it is recommended to append the major version
number to the package name starting from version \c{2.0.0}, for example,
\c{libfoo} (before \c{2.0.0}), \c{libfoo2}, \c{libfoo3} (\c{3.Y.Z}), etc.


\h1#package-version|Package Version|

The \c{bpkg} package version format tries to balance the need of accommodating
existing software versions on one hand and providing a reasonably
straightforward comparison semantics on another. For some background on this
problem see \cb{deb-version(1)} and the \l{http://semver.org Semantic
Versioning} specification.

Note also that if you are strating a new project that will use the \c{build2}
toolchain, then it is strongly recommended that you use the \i{standard
versioning} scheme which is a more strictly defined subset of semanic
versioning and that allows automation of many version management tasks. See
\l{b#module-version Version Module} for details.

The \c{bpkg} package version has the following form:

\
[+<epoch>-]<upstream>[-<prerel>][+<revision>][#<iteration>]
\

The \i{epoch} part should be an integer. It can be used to change to a new
versioning scheme that would be incompatible with the old one. If not
specified, then \i{epoch} defaults to \c{1} except for a stub version (see
below) in which case it defaults to \c{0}. The explicit zero \i{epoch} can be
used if the current versioning scheme (for example, date-based) is known to be
temporary.

The \i{upstream} part is the upstream software version that this package
is based on. It can only contain alpha-numeric characters and \c{'.'}. The
\c{'.'} character is used to separate the version into \i{components}.

The \i{prerel} part is the upstream software pre-release marker, for example,
alpha, beta, candidate, etc. Its format is the same as for \i{upstream} except
for two special values: the absent \i{prerel} (for example, \c{1.2.3})
signifies the maximum or final release while the empty \i{prerel} (for
example, \c{1.2.3-}) signifies the minimum or earliest possible
release. \N{The minimum release is intended to be used for version
constraints (for example, \c{libfoo < 1.2.3-}) rather than actual releases.}

The \i{revision} part should be an integer. It is used to version package
releases that are based on the same upstream versions. If not specified, then
\i{revision} defaults to \c{0}.

The \i{iteration} part is an integer. It is used internally by \c{bpkg} to
automatically version modifications to the packaging information
(specifically, to package manifest and lockfile) in \i{external packages} that
have the same upstream version and revision. As a result, the \i{iteration}
cannot not be specified by the user and is only shown in the \c{bpkg} output
(for example, by \c{pkg-status} command) in order to distinguish between
package iterations with otherwise identical versions. Note also that
\i{iteration} is relative to the \c{bpkg} configuration. Or, in other words,
it is an iteration number of a package as observed by a specific
configuration. As a result, two configuration can \"see\" the same package
state as two different iterations.

\N|Package iterations are used to support package development during which
requiring the developer to manually increment the version or revision after
each modification would be impractical. This mechanism is similar to the
automatic commit versioning provided by the \i{standard version} except that
it is limited to the packaging information but works for uncommitted changes.|

Version \c{+0-0-} (least possible version) is reserved and specifying it
explicitly is illegal. \N{Explicitly specifying this version does not make
much sense since \c{libfoo < +0-0-} is always false and \c{libfoo > +0-0-} is
always true. In the implementation this value is used as a special empty
version.}

Version \c{0} (with a potential revision, for example, \c{0+1}, \c{0+2}) is
used to signify a \i{stub package}. A stub is a package that does not contain
source code and can only be \"obtained\" from other sources, for example, a
system package manager. Note that at some point a stub may be converted into a
full-fledged package at which point it will be assigned a \"real\" version.
It is assumed that this version will always be greater than the stub version.

When displaying the package version or when using the version to derive the
file name, the default \i{epoch} value as well as zero \i{revision} and
\i{iteration} values are omitted (even if they were explicitly specified, for
instance, in the package manifest). For example, \c{+1-1.2.3+0} will be used
as \c{libfoo-1.2.3}.

\N|This versioning scheme and the choice of delimiter characters (\c{.-+})
is meant to align with semantic versioning.|

Some examples of versions:

\
0+1
+0-20180112
1.2.3
1.2.3-a1
1.2.3-b2
1.2.3-rc1
1.2.3-alpha1
1.2.3-alpha.1
1.2.3-beta.1
1.2.3+1
+2-1.2.3
+2-1.2.3-alpha.1+3
+2.2.3#1
1.2.3+1#1
+2-1.2.3+1#2
\

The version sorting order is \i{epoch}, \i{upstream}, \i{prerel},
\i{revision}, and finally, \i{iteration}. The \i{upstream} and \i{prerel}
parts are compared from left to right, one component at a time, as described
next.

To compare two components, first the component types are determined.  A
component that only consists of digits is an integer. Otherwise, it is a
string. If both components are integers, then they are compared as
integers. Otherwise, they are compared lexicographically and
case-insensitively. \N{The reason for case-insensitive comparison is Windows
file names.}

A non-existent component is considered 0 if the other component is an integer
and an empty string if the other component is a string.  For example, in
\c{1.2} vs \c{1.2.0}, the third component in the first version is 0 and the
two versions are therefore equal. As a special exception to this rule, an
absent \i{prerel} part is always greater than any non-absent part. \N{And
thus making the final release always older than any pre-release.}

This algorithm gives correct results for most commonly-used versioning
schemes, for example:

\
1.2.3 < 12.2
1.alpha < 1.beta
20151128 < 20151228
2015.11.28 < 2015.12.28
\

One notable versioning scheme where this approach gives an incorrect result is
hex numbers (consider \c{A} vs \c{1A}). The simplest work around is to convert
such numbers to decimal. Alternatively, one can fix the width of the hex
number and pad all the values with leading zeros, for example: \c{00A} vs
\c{01A}.

It is also possible to convert the \i{upstream} and \i{prerel} parts into a
\i{canonical representation} that will produce the correct comparison result
when always compared lexicographically and as a whole. \N{This can be
useful, for example, when storing versions in the database which would
otherwise require a custom collation implementation to obtain the correct sort
order.}

To convert one of these parts to its canonical representation, all its string
components are converted to the lower case while all its integer components
are padded with leading zeros to the fixed length of \c{16} characters, with
all trailing zero-only components removed. Note that this places an
implementation limit on the length of integer components which should be
checked by the implementation when converting to the canonical
representation. \N{The \c{16} characters limit was chosen to still be able
to represent (with some spare) components in the \i{YYYYMMDDhhmmss} form while
not (visually) bloating the database too much.} As a special case, the absent
\i{prerel} part is represented as \c{'~'}. \N{Since the ASCII code for
\c{'~'} is greater than any other character that could appear in \i{prerel},
such a string will always be greater than any other representation.} The empty
\i{prerel} part is represented as an empty string.

Note that because it is no possible to perform a reverse conversion without
the possibility of loss (consider \c{01.AA.BB}), the original parts may also
have to be stored, for example, for display, to derive package archive names,
etc.

\N|In quite a few contexts the implementation needs to ignore the
\i{revision} and/or \i{iteration} parts. For example, this is needed to
implement the semantics of newer revisions/iterations of packages replacing
their old ones since we do not keep multiple revisions/iterations of the same
upstream version in the same respository. As a result, in the package object
model, we have a version key as just {\i{epoch}, \i{upstream}, \i{prerel}} but
also store the package revision and iteration so that it can be shown it to
the user, etc.|

\h1#manifests|Manifests|

This chapter describes the general manifest file format as well as the
concrete manifests used by \c{bpkg}.

Currently, three manifests are defined: package manifest, repository manifest,
and signature manifest. The former two manifests can also be combined into a
list of manifests to form the list of available packages and the description
of a repository, respectively.

\h#manifest-format|Manifest Format|

The manifest format is a UTF-8 encoded text containing a list of name-value
pairs in the form:

\
<name>: <value>
\

For example:

\
name: libfoo
version: 1.2.3
\

The name can contain any characters except \c{':'} and whitespaces. Newline
terminates the pair unless escaped with \c{'\'} (see below). Leading and
trailing whitespaces before and after name and value are ignored except in the
multi-line mode (see below).

If, the first non-whitespace character on the line is \c{'#'}, then the rest
of the line is treated as a comment and ignored except if the preceding
newline was escaped or in the multi-line mode (see below). For example:

\
# This is a comment.
short: This is #not a comment
long: Also \
#not a comment
\

The first name-value pair in the manifest file should always have an empty
name. The value of this special pair is the manifest format version. The
version value shall use the default (that is, non-multi-line) mode and shall
not use any escape sequences. Currently it should be \c{1}, for example:

\
: 1
name: libfoo
version: 1.2.3
\

Any new name that is added without incrementing the version must be optional
so that it can be safely ignored by older implementations.

The special empty name pair can also be used to separate multiple
manifests. In this case the version may be omitted in the subsequent
manifests, for example:

\
: 1
name: libfoo
version: 1.2.3
:
name: libbar
version: 2.3.4
\

To disable treating of a newline as a name-value pair terminator we can escape
it with \c{'\'}. Note that \c{'\'} is only treated as an escape sequence when
followed by a newline and both are simply removed from the stream (as opposed
to being replaced which a space). To enter a literal \c{'\'} at the end of the
value, use the \c{'\\'} sequence. For example:

\
description: Long text that doesn't fit into one line \
so it is continued on the next line.
\

\
windows-path: C:\foo\bar\\
\

Notice that in the final example only the last \c{'\'} needs special handling
since it is the only one that is followed by a newline.

One may notice that in this newline escaping scheme a line consisting of just
\c{'\'} followed by a newline has no use, except, perhaps, for visual
presentation of, arguably, dubious value. For example, this representation:

\
description: First line. \
\\
Second line.
\

Is semantically equivalent to:

\
description: First line. Second line.
\

As a result, such a sequence is \"overloaded\" to provide more useful
functionality in two ways: Firstly, if \c{':'} after the name is immediately
followed (ignoring whitespaces) by \c{'\'} and a newline, then it signals the
start of the multi-line mode. In this mode all subsequent newlines and \c{'#'}
are treated as ordinary characters rather than value terminators or comments
until a line consisting of just '\' and a newline (the multi-line mode
terminator). For example:

\
description:\
First paragraph.
#
Second paragraph.
\\
\

Expressed as a C-string, the value in the above example is:

\
\"First paragraph.\n#\nSecond paragraph.\"
\


\N|If we didn't expect to ever need to specify a name with an empty value,
then an empty value could have turned on the multi-line mode, for example:

\
description:
First paragraph.
#
Second paragraph.
\\
\

There are two reasons we don't do this: we don't want to close the door on
empty values and we want a more explicit \"introductor\" for the multi-line
mode since it is quite different compared to the simple mode.|

Note that in the multi-line mode we can still use newline escaping to split
long lines, for example:

\
description:\
First paragraph that doesn't fit into one line \
so it is continued on the next line.
Second paragraph.
\\
\

In the simple (that is, non-multi-line) mode, the sole \c{'\'} and newline
sequence is overloaded to mean a newline. So the previous example can also be
represented like this:

\
description: First paragraph that doesn't fit into one \
line so it is continued on the next line.\
\\
Second paragraph.
\

Note that the multi-line mode can be used to capture a value with leading
and/or trailing whitespaces, for example:

\
description:\
  test

\\
\

The C-string representing this value is:

\
\"  test\n\"
\

EOF can be used instead of a newline to terminate both simple and multi-line
values. For example the following representation results in the same value as
in the previous example.

\
description:\
  test

<EOF>
\

By convention, names are all in lower case and multi-word names are separated
with \c{'-'}. Note that names are case-sensitive.

Also by convention, the following name suffixes are used to denote common
types of values:

\
-file
-url
-email
\

For example:

\
description: Inline description
description-file: README
package-url: http://www.example.com
package-email: john@example.com
\

Other common name suffixes (such as -feed) could be added later.

\N|Generally, unless there is a good reason not to, we keep values
lower-case (for example, \c{requires} values such as \c{c++11} or
\c{linux}). An example where we use upper/mixed case would be \c{license}; it
seems unlikely \c{gplv2} would be better than \c{GPLv2}.|

A number of name-value pairs described below allow for the value proper to be
optionally followed by ';' and a comment. Such comments serve as additional
documentation for the user and should be full sentence(s), that is start with
a capital letter and end with a period. Note that unlike \c{#}-style comments
which are ignored, these comments are considered to be part of the value. For
example:

\
email: foo-users@example.com; Public mailing list.
\

It is recommended that you keep comments short, single-sentence. Note that
non-comment semicolons in such values have to be escape with a backslash, for
example:

\
url: http://git.example.com/?p=foo\;a=tree
\

In the manifest specifications described below optional components are
enclosed in square brackets (\c{[]}). If the name is enclosed in \c{[]} then
the name-value pair is optional, otherwise \- required. For example:

\
name: <name>
license: <licenses> [; <comment>]
[description]: <text>
\

In the above example \c{name} is required, \c{license} has an optional
component (comment), and \c{description} is optional.

In certain situations (for example, shell scripts) it can be easier to parse
the binary manifest representation. The binary representation does not include
comments and consists of a sequence of name-value pairs in the following form:

\
<name>:<value>\0
\

That is, the name and the value are separated by a colon and each pair
(including the last) is terminated with the \c{NUL} character. Note that there
can be no leading or trailing whitespace characters around the name and any
whitespaces after the colon and before the \c{NUL} terminator are part of the
value.


\h#manifest-package|Package Manifest|

The package manifest (the \c{manifest} file found in the package's root
directory) describes a \c{bpkg} package. The manifest synopsis is presented
next followed by the detailed description of each value in subsequent
sections.

\
name: <name>
version: <version>
[project]: <name>
[priority]: <priority> [; <comment>]
summary: <text>
license: <licenses> [; <comment>]
[tags]: <tags>
[description]: <text>
[description-file]: <path> [; <comment>]
[changes]: <text>
[changes-file]: <path> [; <comment>]

[url]: <url> [; <comment>]
[doc-url]: <url> [; <comment>]
[src-url]: <url> [; <comment>]
[package-url]: <url> [; <comment>]

[email]: <email> [; <comment>]
[package-email]: <email> [; <comment>]
[build-email]: <email> [; <comment>]

[depends]: [?][*] <alternatives> [; <comment>]
[requires]: [?] [<alternatives>] [; <comment>]

[build-include]: <config>[/<target>] [; <comment>]
[build-exclude]: <config>[/<target>] [; <comment>]
\

\h2#manifest-package-name|\c{name}|

\
name: <name>
\

The package name. See \l{#package-name Package Name} for the package name
format description. Note that the name case is preserved for display, in file
names, etc.


\h2#manifest-package-version|\c{version}|

\
version: <version>
\

The package version. See \l{#package-version Package Version} for the version
format description. Note that the version case is preserved for display, in
file names, etc.


\h2#manifest-package-project|\c{project}|

\
[project]: <name>
\

The project this package belongs to. The project name has the same
restrictions as the package name (see \l{#package-name Package Name} for
details) and its case is preserved for display, in directory names, etc. If
unspecified, then the project name is assumed to be the same as the package
name.

Projects are used to group related packages together in order to help with
organization and discovery in repositories. For example, packages \c{hello},
\c{libhello}, and \c{libhello2} could all belong to project \c{hello}. By
convention, projects of library packages are named without the \c{lib} prefix.


\h2#manifest-package-|\c{priority}|

\
[priority]: <priority> [; <comment>]

<priority> = security | high | medium | low
\

The release priority (optional). As a guideline, use \c{security} for security
fixes, \c{high} for critical bug fixes, \c{medium} for important bug fixes,
and \c{low} for minor fixes and/or feature releases. If not specified, \c{low}
is assumed.


\h2#manifest-package-summary|\c{summary}|

\
summary: <text>
\

The short description of the package.


\h2#manifest-package-license|\c{license}|

\
license: <licenses> [; <comment>]

<licenses> = <license> [, <license>]*
\

The package lincense. The format is a comma-separated list of license names
under which this package is distributed. This list has the \i{AND} semantics,
that is, the user must comply with all the licenses listed. To capture
alternative licensing options use multiple \c{license} values, for example:

\
license: LGPLv2, MIT
license: BSD
\

In the above example, the package can be used either under the BSD license or
both LGPLv2 and MIT.

For complex licensing schemes it is recommended to add comments as an aid to
the user, for example:

\
license: LGPLv2, MIT; If linking with GNU TLS.
license: BSD;         If linking with OpenSSL.
\

To assist automated processing, the following pre-defined values should be
used for the common licenses:

\
MIT
GPLv2
GPLv3
LGPLv2
LGPLv3
ASLv1         ; Apache License 1.0.
ASLv1.1       ; Apache License 1.1.
ASLv2         ; Apache License 2.0.
BSD           ; BSD 3-clause.
BSD-Original  ; BSD original.

public domain
available source ; Not free software/open source.
proprietary
\

\N|An example of automated processing would be filtering for non-copyleft
licensed packages.|

\h2#manifest-package-tags|\c{tags}|

\
[tags]: <tags>

<tags> = <tag> [, <tag>]*
\

The package tags (optional). The format is a comma-separated list of words
that describe this package.

\N|Originally, support for multi-word tags were considered, however this
quickly degenerated into quite a complex functionality. In particular, in such
a case we should probably treat multi-word tags as if the single word as well
as shorter, multi-word derivations were also mentioned. That is, \"xml pull
parser\" should be equivalent to \"xml pull parser, xml pull, xml parser,
pull parser, xml, pull, parser\".

On the user side, if exact phrase matches are favored, then this serves as an
encouragement to come up with ever more elaborate multi-word tags to \"cover\"
as much ground as possible. For example, \"streaming c++ xml pull parser\".

As a result, we will start simple and only allow single-word tags.|


\h2#manifest-package-description|\c{description}|

\
[description]: <text>
[description-file]: <path> [; <comment>]
\

The detailed description of the package. It can be provided either inline as a
text fragment or by referring to a file within a package (e.g., \c{README}),
but not both.

In the web interface (\c{brep}) the description is formatted into one or more
paragraphs using blank lines as paragraph separators. Specifically, it is not
represented as \c{<pre>} so any kind of additional plain text formatting (for
example, lists) will be lost and should not be used in the description.


\h2#manifest-package-changes|\c{changes}|

\
[changes]: <text>
[changes-file]: <path> [; <comment>]
\

The description of changes in the release.

\N|The tricky aspect is what happens if the upstream release stays the
same (and has, say, a \c{NEWS} file to which we point) but we need to make
another package release, for example, to apply a critical patch.|

Multiple \c{changes} values can be present which are all concatenated in the
order specified, that is, the first value is considered to be the most recent
(similar to \c{ChangeLog} and \c{NEWS} files). For example:

\
changes: 1.2.3-2: applied upstream patch for critical bug bar
changes: 1.2.3-1: applied upstream patch for critical bug foo
changes-file: NEWS
\

Or:

\
changes:\
1.2.3-2
  - applied upstream patch for critical bug bar
  - regenerated documentation

1.2.3-1
  - applied upstream patch for critical bug foo
\\
changes-file: NEWS
\

In the web interface (\c{brep}) the changes are displayed as pre-formatted
plain text. \N{We could use the comment to \"hint\" at the file format.}


\h2#manifest-package-url|\c{url}|

\
[url]: <url> [; <comment>]
\

The project home page URL.


\h2#manifest-package-doc-url|\c{doc-url}|

\
[doc-url]: <url> [; <comment>]
\

The project documentation URL.


\h2#manifest-package-src-url|\c{src-url}|

\
[src-url]: <url> [; <comment>]
\

The project source repository URL.


\h2#manifest-package-package-url|\c{package-url}|

\
[package-url]: <url> [; <comment>]
\

The package home page URL. If not specified, then assumed to be the same as
\c{url}. It only makes sense to specify this value if the project and
package are maintained separately.


\h2#manifest-package-email|\c{email}|

\
[email]: <email> [; <comment>]
\

The project email address. For example, a support mailing list.


\h2#manifest-package-package-email|\c{package-email}|

\
[package-email]: <email> [; <comment>]
\

The package email address. If not specified, then assumed to be the same as
\c{email}. It only makes sense to specify this value if the project and
package are maintained separately.


\h2#manifest-package-build-email|\c{build-email}|

\
[build-email]: <email> [; <comment>]
\

The build notification email address. It is used to send build result
notifications by automated build bots. If not specified, then assumed to be
the same as \c{package-email}. If specified but empty, then no build result
notifications for this package are sent by email.

\h2#manifest-package-depends|\c{depends}|

\
[depends]: [?][*] <alternatives> [; <comment>]

<alternatives> := <dependency> [ '|' <dependency>]*
<dependency>   := <name> [<constraint>]
<constraint>   := <comparison> | <shortcut> | <range>
<comparison>   := ('==' | '>' | '<' | '>=' | '<=') <version>
<shortcut>     := ('^' | '~') <version>
<range>        := ('(' | '[') <version> <version> (')' | ']')
\

The prerequisite packages. If the \c{depends} value start with \c{'*'}, then
it is a \i{build-time} prerequisite. Otherwise it is \i{run-time}.

\N|Most of the build-time prerequisites are expected to be tools such as code
generator, so you can think of \c{'*'} as the executable mark printed by
\c{ls}. An important difference between the two kind of dependencies is that
in case of cross-compilation a build-time dependency must be built for the
build machine, not the target.|

Two special build-time dependency names are recognized and checked in an ad
hoc manner: \c{build2} (the \c{build2} build system) and \c{bpkg} (the
\c{build2} package manager). This allows us to specify the required build
system and package manager versions, for example:

\
depends: * build2 >= 0.6.0
depends: * bpkg >= 0.6.0
\

Each \c{depends} value can specify multiple packages with the \i{OR}
semantics. While multiple \c{depends} values are used to specify multiple
packages with the \i{AND} semantics. A value that starts with \c{'?'} is a
conditional prerequisite. Whether such a prerequisite will be in effect can
only be determined at the package configuration time. It is recommended that
you provide a comment for each conditional prerequisite as an aid to the user.
For example:

\
depends: libz
depends: libfoo ~1.2.0; Only works with libfoo 1.2.*.
depends: libgnutls >= 1.2.3 | libopenssl >= 2.3.4
depends: ? libboost-regex >= 1.52.0; Only if no C++11 <regex>.
depends: ? libqtcore >= 5.0.0; Only if GUI is enabled.
\

It is recommended that you specify unconditional dependencies first with
simple (no alternatives) dependencies leading each set.

The optional version constraint can be specified using comparison operators,
shortcut (to range) operators, and ranges.

The shortcut operators can only be used with \l{b#module-version standard
versions} (a semantic version without the pre-release part is a standard
version). They are equivalent to the following ranges. \N{The \c{X.Y.Z-} version
signifies the earliest pre-release in the \c{X.Y.Z} series; see
\l{#package-version Package Version} for details}.

\
~X.Y.Z  [X.Y.Z  X.Y+1.0-)

^X.Y.Z  [X.Y.Z  X+1.0.0-)  if X >  0
^0.Y.Z  [0.Y.Z  0.Y+1.0-)  if X == 0
\

That is, the tilde (\c{~}) constraint allows upgrades to any further patch
version while the caret (\c{^}) constraint \- also to any further minor
version.

\N|Zero major version component is customarily used during early development
where the minor version effectively becomes major. As a result, the tilde
constraint has special semantics for this case.|

Note that the shortuct operators can only be used with the complete,
three-component versions (\c{X.Y.Z} with the optional pre-release part per the
standard version). Specifically, there is no support for special \c{^X.Y} or
\c{~X} semantics offered by some package manager \- if desired, such
functionality can be easily achieved with ranges. Also, the \c{0.0.Z} version
is not considered special except as having zero major component for the tilde
semantics discussed above.

Note also that pre-releases do not required any special considerations when
used with the shortcut operators. For example, if package \c{libfoo} is
usable starting with the second beta of the \c{2.0.0} release, then our
constraint could be expressed as:

\
depends: libfoo ^2.0.0-b.2
\

\N|Internally shortucts and comparisons can be represented as ranges (that is,
\c{[v, v]} for \c{==}, \c{(v, inf)} for \c{>}, etc). However, for display and
serialization such representations should be converted back to simple
operators. While it is possible that the original manifest specified equality
or shortucts as full ranges, it is acceptable to display/serialize them as
simpler operators.|

\h2#manifest-package-requires|\c{requires}|

\
[requires]: [?] [<alternatives>] [; <comment>]

<alternatives> := <requirement> [ '|' <requirement>]*
<requirement>  := <id> | <dependency>
\

The package requirements (other than other packages). Such requirements are
normally checked during package configuration by the build system and the only
purpose of capturing them in the manifest is for documentation. Similar to
\c{depends}, a value that starts with \c{'?'} is a conditional
requirement. For example:

\
requires: linux | windows | macosx
requires: c++11
requires: ? ; VC 15 or later if targeting Windows.
requires: ? ; libc++ if using Clang on Mac OS.
\

Note that \c{requires} should also be used to specify dependencies on external
libraries, that is, then ones not packaged or not in the repository. In this
case it may make sense to also specify the version constraint. For example:

\
requires: zlib >= 1.2.0; Most systems already have it or get from zlib.net.
\

It is recommended that you specify unconditional requirements first with
simple (no alternatives) requirements leading each set.

To assist automated processing, the following pre-defined ids should be used
for the common requirements:

\
c++98
c++03
c++11
c++14
c++17
c++21
\

\
posix
linux
macos
freebsd
windows
\

\
gcc[_X.Y.Z]  ; For example: gcc_6, gcc_4.9, gcc_5.0.0
clang[_X.Y]  ; For example: clang_6, clang_3.4, clang_3.4.1
msvc[_NU]    ; For example: msvc_14, msvc_15u3
\

\h2#manifest-package-include-exclude|\c{build-{include,exclude\}}|

\
[build-include]: <config>[/<target>] [; <comment>]
[build-exclude]: <config>[/<target>] [; <comment>]
\

The package build inclusions and exclusions. The \c{build-include} and
\c{build-exclude} values specify the build configurations and, optionally,
targets the package should or should not be built for by automated build
bots. The \i{config} and \i{target} values are filesystem wildcard patterns
which are matched against the build configuration names and target names (see
the \c{bbot} documentation for details).

The exclusion and inclusion patterns are applied in the order specified with
the first match determining whether the package will be built for this
configuration and target. If none of the patterns match (or none we
specified), then the package is built.

As an example, the following value will exclude 32-bit builds for the VC14
compiler:

\
build-exclude: *-msvc_14*/i?86-* ; Linker crash.
\

As another example, the following pair of values will make sure that a package
is only built on Linux:

\
build-include: linux*
build-exclude: * ; Only supported on Linux.
\

Note that the comment of the matching exclusion is used by the web interface
(\c{brep}) to display the reason for the build exclusion.


\h#manifest-package-list-pkg|Package List Manifest for \cb{pkg} Repositories|

The package list manifest (the \c{packages.manifest} file found in the
\cb{pkg} repository root directory) describes the list of packages available
in the repository. First comes a manifest that describes the list itself
(referred to as the list manifest). The list manifest synopsis is presented
next:

\
sha256sum: <sum>
\

After the list manifest comes a (potentially empty) sequence of package
manifests. These manifests shall not contain any \c{*-file} values (such
values should be converted to their inline versions) but must contain the
following additional (to package manifest) values:

\
location: <path>
sha256sum: <sum>
\

The detailed description of each value follows in the subsequent sections.

\h2#manifest-package-list-pkg-sha256sum|\c{sha256sum} (list manifest)|

\
sha256sum: <sum>
\

The SHA256 checksum of the \c{repositories.manifest} file (described below)
that corresponds to this repository. The \i{sum} value should be 64
characters long (that is, just the SHA256 value, no file name or any other
markers), be calculated in the binary mode, and use lower-case letters.

\N|This checksum is used to make sure that the \c{repositories.manifest}
file that was fetched is the same as the one that was used to create the
\c{packages.manifest} file. This also means that if \c{repositories.manifest}
is modified in any way, then \c{packages.manifest} must be regenerated as
well.|

\h2#manifest-package-list-pkg-package-location|\c{location} (package manifest)|

\
location: <path>
\

The path to the package archive file relative to the repository root. It
should be in the POSIX representation.

\N|if the repository keeps multiple versions of the package and places
them all into the repository root directory, it can get untidy. With
\c{location} we allow for sub-directories.|


\h2#manifest-package-list-pkg-package-sha256sum|\c{sha256sum} (package manifest)|

\
sha256sum: <sum>
\

The SHA256 checksum of the package archive file. The \i{sum} value should be
64 characters long (that is, just the SHA256 value, no file name or any other
markers), be calculated in the binary mode, and use lower-case letters.


\h#manifest-package-list-dir|Package List Manifest for \cb{dir} Repositories|

The package list manifest (the \c{packages.manifest} file found in the
\cb{dir} repository root directory) describes the list of packages available
in the repository. It is a (potentially empty) sequence of manifests with the
following synopsis:

\
location: <path>
[fragment]: <string>
\

The detailed description of each value follows in the subsequent sections.
The \c{fragment} value can only be present in a merged \c{packages.manifest}
file for a multi-fragment repository.

As an example, if our repository contained the \c{src/} subdirectory that in
turn contained the \c{libfoo} and \c{foo} packages, then the corresponding
\c{packages.manifest} file could look like this:

\
: 1
location: src/libfoo/
:
location: src/foo/
\

\h2#manifest-package-list-dir-location|\c{location}|

\
location: <path>
\

The path to the package directory relative to the repository root. It should
be in the POSIX representation.


\h2#manifest-package-list-dir-fragment|\c{fragment}|

\
[fragment]: <string>
\

The repository fragment id this package belongs to.


\h#manifest-repository|Repository Manifest|

The repository manifest (only used as part of the repository manifest list
described below) describes a \cb{pkg}, \cb{dir}, or \cb{git} repository. The
manifest synopsis is presented next followed by the detailed description of
each value in subsequent sections.

\
[location]: <uri>
[type]: pkg|dir|git
[role]: base|prerequisite|complement
[trust]: <fingerprint>
[url]: <url>
[email]: <email> [; <comment>]
[summary]: <text>
[description]: <text>
[certificate]: <pem>
[fragment]: <string>
\

See also the Repository Chaining documentation for further information @@ TODO.

\h2#manifest-repository-location|\c{location}|

\
[location]: <uri>
\

The repository location. The location can only and must be omitted for the
base repository. \N{Since we got hold of its manifest, then we presumably
already know the location of the base repository.} If the location is a
relative path, then it is treated as relative to the base repository location.

For the \cb{git} repository type the relative location does not inherit the
URL fragment from the base repository. Note also that the remote \cb{git}
repository locations normally have the \cb{.git} extension that is stripped
when a repository is cloned locally. To make the relative locations usable in
both contexts, the \cb{.git} extension should be ignored if the local
prerequisite repository with the extension does not exist while the one
without the extension does.

While POSIX systems normally only support POSIX paths (that is, forward
slashes only), Windows is generally able to handle both slash types. As a
result, it is recommended that POSIX paths are always used in the \c{location}
values, except, perhaps, if the repository is explicitly Windows-only by, for
example, having a location that is an absolute Windows path with the drive
letter. \N{The \cb{bpkg} package manager will always try to represent the
location as a POSIX path and only fallback to the native representation if
that is not possible (for example, there is a drive letter in the path).}


\h2#manifest-repository-type|\c{type}|

\
[type]: pkg|dir|git
\

The repository type. The type must be omitted for the base repository. If the
type is omitted for a prerequisite/complement repository, then it is guessed
from its \c{location} value as described in \l{bpkg-rep-add(1)}.


\h2#manifest-repository-role|\c{role}|

\
[role]: base|prerequisite|complement
\

The repository role. The \c{role} value can be omitted for the base
repository only.


\h2#manifest-repository-trust|\c{trust}|

\
[trust]: <fingerprint>
\

The repository fingerprint to trust. The \c{trust} value can only be specified
for prerequisite and complement repositories and only for repository types
that support authentication (currently only \c{pkg}). The \i{fingerprint}
value should be an SHA256 repository fingerprint represented as 32
colon-separated hex digit pairs. \N{The repository in question is only trusted
for use as a prerequisite or complement of this repository. If it is also used
by other repositories or is added to the configuration by the user, then such
uses cases are authenticated independently.}


\h2#manifest-repository-url|\c{url}|

\
[url]: <url>
\

The repository's web interface (\c{brep}) URL. It can only be specified for
the base repository (the web interface URLs for prerequisite/complement
repositories can be extracted from their respective manifests).

For example, given the following \c{url} value:

\
url: https://example.org/hello/
\

The package details page for \c{libfoo} located in this repository will be
\c{https://example.org/hello/libfoo}.

The web interface URL can also be specified as relative to the repository
location (the \c{location} value). In this case \i{url} should start with two
path components each being either \c{.} or \c{..}. If the first component is
\c{..}, then the \c{www}, \c{pkg} or \c{bpkg} domain component, if any, is
removed from the \c{location} URL host, just like when deriving the repository
name.

Similarly, if the second component is \c{..}, then the \c{pkg} or \c{bpkg}
path component, if any, is removed from the \c{location} URL path, again, just
like when deriving the repository name.

Finally, the version component is removed from the \c{location} URL path, the
rest (after the two \c{.}/\c{..} components) of the \c{url} value is appended
to it, and the resulting path is normalized with all remaining \c{..}  and
\c{.} applied normally.

For examples, assuming repository location is:

\
https://pkg.example.org/test/pkg/1/hello/stable
\

The following listing shows some of the possible combinations (the \c{<>}
marker is used to highlight the changes):

\
./.          ->  https://pkg.example.org/test/pkg/hello/stable
../.         ->  https://<  >example.org/test/pkg/hello/stable
./..         ->  https://pkg.example.org/test/<  >hello/stable
../..        ->  https://<  >example.org/test/<  >hello/stable
././..       ->  https://pkg.example.org/test/pkg/hello<     >
../../../..  ->  https://<  >example.org/test<               >
\

\N|The rationale for the relative web interface URLs is to allow
deployment of the same repository to slightly different configuration, for
example, during development, testing, and public use. For instance, for
development we may use the \c{https://example.org/pkg/} setup while in
production it becomes \c{https://pkg.example.org/}. By specifying the web
interface location as, say, \c{../.}, we can run the web interface at
these respective locations using a single repository manifest.|


\h2#manifest-repository-email|\c{email}|

\
[email]: <email> [; <comment>]
\

The repository email address. It must and can only be specified for the base
repository. The email address is displayed by the web interface (\c{brep}) in
the repository about page and could be used to contact the maintainers about
issues with the repository.


\h2#manifest-repository-summary|\c{summary}|

\
[summary]: <text>
\

The short description of the repository. It must and can only be specified for
the base repository.


\h2#manifest-repository-description|\c{description}|

\
[description]: <text>
\

The detailed description of the repository. It can only be specified for the
base repository.

In the web interface (\c{brep}) the description is formatted into one or more
paragraphs using blank lines as paragraph separators, similar to the package
description.


\h2#manifest-repository-certificate|\c{certificate}|

\
[certificate]: <pem>
\

The X.509 certificate for the repository. It should be in the PEM format and
can only be specified for the base repository. Currently only used for the
\cb{pkg} repository type.

The certificate should contain the \c{CN} and \c{O} components in the subject
as well as the \c{email:} component in the subject alternative names. The
\c{CN} component should start with \c{name:} and continue with the repository
name prefix/wildcard (without trailing slash) that will be used to verify the
repository name(s) that are authenticated with this certificate. See
\l{bpkg-repository-signing(1)} for details.

If this value is present then the \c{packages.manifest} file must be signed
with the corresponding private key and the signature saved in the
\c{signature.manifest} file. See \l{#manifest-signature-pkg Signature
Manifest} for details.


\h2#manifest-repository-fragment|\c{fragment}|

\
[fragment]: <string>
\

The repository fragment id this repository belongs to.


\h#manifest-repository-list|Repository List Manifest|

@@ TODO See the Repository Chaining document for more information on the
terminology and semantics.

The repository list manifest (the \c{repositories.manifest} file found in the
repository root directory) describes the repository. It is a sequence of
repository manifests consisting of the base repository manifest (that is, the
manifest for the repository that is being described) as well as manifests for
its prerequisite and complement repositories. The individual repository
manifests can appear in any order and the base repository manifest can be
omitted.

The \c{fragment} values can only be present in a merged
\c{repositories.manifest} file for a multi-fragment repository.

As an example, a repository manifest list for the \c{math/testing}
repository could look like this:

\
# math/testing
#
: 1
email: math-pkg@example.org
summary: Math package repository
:
role: complement
location: ../stable
:
role: prerequiste
location: https://pkg.example.org/1/misc/testing
\

Here the first manifest describes the base repository itself, the second
manifest \- a complement repository, and the third manifest \- a prerequisite
repository. Note that the complement repository's location is specified as a
relative path. For example, if the base repository location were:

\
https://pkg.example.org/1/math/testing
\

Then the completement's location would be:

\
https://pkg.example.org/1/math/stable
\


\h#manifest-signature-pkg|Signature Manifest for \cb{pkg} Repositories|

The signature manifest (the \c{signature.manifest} file found in the \cb{pkg}
repository root directory) contains the signature of the repository's
\c{packages.manifest} file. In order to detect the situation where the
downloaded \c{signature.manifest} and \c{packages.manifest} files belong to
different updates, the manifest contains both the checksum and the signature
(which is the encrypted checksum). \N{We cannot rely on just the signature
since a mismatch could mean either a split update or tampering.} The manifest
synopsis is presented next followed by the detailed description of each value
in subsequent sections.

\
sha256sum: <sum>
signature: <sig>
\

\h2#manifest-signature-pkg-sha256sum|\c{sha256sum}|

\
sha256sum: <sum>
\

The SHA256 checksum of the \c{packages.manifest} file. The \i{sum} value
should be 64 characters long (that is, just the SHA256 value, no file name or
any other markers), be calculated in the binary mode, and use lower-case
letters.


\h2#manifest-signature-pkg-signature|\c{signature}|

\
signature: <sig>
\

The signature of the \c{packages.manifest} file. It should be calculated by
encrypting the above \c{sha256sum} value with the repository certificate's
private key and then \c{base64}-encoding the result.
"

//@@ TODO items (grep).
//@@ TODO: repository chaining, fix link in #manifest-repostiory.
//@@ TODO: complete license list (MPL, ...)
//@@ Are there any restrictions on requires ids? Is this valid: msvc >= 15u3?