Add version guessing function to gitdir and cached repo.

Change-Id: I1c79ce68a7a7534d36a9e83210e18a58e7b648e8

2 files changed, 15 insertions, 0 deletions

diff --git a/morphlib/cachedrepo.py b/morphlib/cachedrepo.py
index 0c0f5cb7..a630cc29 100644
--- a/morphlib/cachedrepo.py
+++ b/morphlib/cachedrepo.py
@@ -143,6 +143,15 @@ class CachedRepo(object):
         '''
         return self._gitdir.branches_containing_sha1(ref)
 
+    def version_guess(self, ref): # pragma: no cover
+        '''Guess version number using `git describe --tags`
+
+        Raises a gitdir.InvalidRefError if the ref is not found in the
+        repository.
+
+        '''
+        return self._gitdir.version_guess(ref)
+
     def list_files(self, ref, recurse=True):  # pragma: no cover
         '''Return filenames found in the tree pointed to by the given ref.
 
diff --git a/morphlib/gitdir.py b/morphlib/gitdir.py
index 1c286720..a6dd26a1 100644
--- a/morphlib/gitdir.py
+++ b/morphlib/gitdir.py
@@ -707,6 +707,12 @@ class GitDirectory(object):
         args = ['branch', '--contains', ref]
         return self._gitcmd_output_list(*args)
 
+    def version_guess(self, ref): # pragma: no cover
+        self._check_ref_exists(ref)
+
+        args = ['describe', '--tags', '--always', ref]
+        return morphlib.git.gitcmd(self._runcmd, *args).strip()
+
     def _update_ref(self, ref_args, message):
         args = ['update-ref']
         # No test coverage, since while this functionality is useful,