Add git utility functions

1 files changed, 89 insertions, 0 deletions

diff --git a/libbutl/git.cxx b/libbutl/git.cxx
new file mode 100644
index 0000000..bb5f542
--- /dev/null
+++ b/libbutl/git.cxx
@@ -0,0 +1,89 @@
+// file      : libbutl/git.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2018 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef __cpp_modules
+#include <libbutl/git.mxx>
+#endif
+
+// C includes.
+
+#include <cassert>
+
+#ifndef __cpp_lib_modules
+#include <string>
+
+#include <cstddef> // size_t
+#endif
+
+// Other includes.
+
+#ifdef __cpp_modules
+module butl.git;
+
+// Only imports additional to interface.
+#ifdef __clang__
+#ifdef __cpp_lib_modules
+import std.core;
+#endif
+import butl.path;
+import butl.optional;
+import butl.standard_version
+#endif
+
+import butl.utility;    // digit()
+import butl.filesystem; // entry_exists()
+#else
+#include <libbutl/utility.mxx>
+#include <libbutl/optional.mxx>
+#include <libbutl/filesystem.mxx>
+#include <libbutl/standard-version.mxx>
+#endif
+
+using namespace std;
+
+namespace butl
+{
+  bool
+  git_repository (const dir_path& d)
+  {
+    // .git can be either a directory or a file in case of a submodule or a
+    // separate working tree.
+    //
+    return entry_exists (d / ".git",
+                         true /* follow_symlinks */,
+                         true /* ignore_errors   */);
+  }
+
+  optional<standard_version>
+  git_version (const string& s)
+  {
+    // There is some variety across platforms in the version
+    // representation.
+    //
+    // Linux:  git version 2.14.3
+    // MacOS:  git version 2.10.1 (Apple Git-78)
+    // MinGit: git version 2.16.1.windows.1
+    //
+    // We will consider the first 3 version components that follows the
+    // common 'git version ' prefix.
+    //
+    const size_t b (12);
+    if (s.compare (0, b, "git version ") == 0)
+    {
+      size_t i (b);
+      size_t n (0);
+      for (char c; i != s.size () && (digit (c = s[i]) || c == '.'); ++i)
+      {
+        if (c == '.' && ++n == 3)
+          break;
+      }
+
+      // Returns nullopt if fail to parse.
+      //
+      return parse_standard_version (string (s, b, i - b));
+    }
+
+    return nullopt;
+  }
+}