1 files changed, 106 insertions, 0 deletions
diff --git a/build2/version/snapshot-git.cxx b/build2/version/snapshot-git.cxx
new file mode 100644
index 0000000..b5db470
--- /dev/null
+++ b/build2/version/snapshot-git.cxx
@@ -0,0 +1,106 @@
+// file      : build2/version/snapshot-git.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <build2/version/snapshot>
+
+using namespace std;
+
+namespace build2
+{
+  namespace version
+  {
+    snapshot
+    extract_snapshot_git (const dir_path& src_root)
+    {
+      snapshot r;
+      const char* d (src_root.string ().c_str ());
+
+      // First check whether the working directory is clean. There doesn't
+      // seem to be a way to do everything in a single invocation (the
+      // porcelain v2 gives us the commit id but not timestamp).
+      //
+
+      // If git status --porcelain returns anything, then the working
+      // directory is not clean.
+      //
+      {
+        const char* args[] {"git", "-C", d, "status", "--porcelain", nullptr};
+
+        if (!run<string> (args, [] (string& s) {return move (s);}).empty ())
+          return r;
+      }
+
+      // Now extract the commit id and date.
+      //
+      auto extract = [&r] (string& s) -> snapshot
+      {
+        if (s.compare (0, 5, "tree ") == 0)
+        {
+          // The 16-characters abbreviated commit id.
+          //
+          r.id.assign (s, 5, 16);
+
+          if (r.id.size () != 16)
+            fail << "unable to extract git commit id from '" << s << "'";
+        }
+        else if (s.compare (0, 10, "committer ") == 0)
+        try
+        {
+          // The line format is:
+          //
+          // committer <noise> <timestamp> <timezone>
+          //
+          // For example:
+          //
+          // committer John Doe <john@example.org> 1493117819 +0200
+          //
+          // The timestamp is in seconds since UNIX epoch. The timezone
+          // appears to be always numeric (+0000 for UTC).
+          //
+          size_t p1 (s.rfind (' ')); // Can't be npos.
+          string tz (s, p1 + 1);
+
+          size_t p2 (s.rfind (' ', p1 - 1));
+          if (p2 == string::npos)
+            throw invalid_argument ("missing timestamp");
+
+          string ts (s, p2 + 1, p1 - p2 - 1);
+          r.sn = stoull (ts);
+
+          if (tz.size () != 5)
+            throw invalid_argument ("invalid timezone");
+
+          unsigned long h (stoul (string (tz, 1, 2)));
+          unsigned long m (stoul (string (tz, 3, 2)));
+          unsigned long s (h * 3600 + m * 60);
+
+          // The timezone indicates where the timestamp was generated so
+          // to convert to UTC we need to invert the sign.
+          //
+          switch (tz[0])
+          {
+          case '+': r.sn -= s; break;
+          case '-': r.sn += s; break;
+          default: throw invalid_argument ("invalid timezone sign");
+          }
+        }
+        catch (const invalid_argument& e)
+        {
+          fail << "unable to extract git commit date from '" << s << "': " << e;
+        }
+
+        return (r.id.empty () || r.sn == 0) ? snapshot () : move (r);
+      };
+
+      const char* args[] {
+        "git", "-C", d, "cat-file", "commit", "HEAD", nullptr};
+      r = run<snapshot> (args, extract);
+
+      if (r.empty ())
+        fail << "unable to extract git commit id/date for " << src_root;
+
+      return r;
+    }
+  }
+}