Bug 1505634 - Allow MOZ_ARTIFACT_REVISION to point to unknown mercurial changesets. r=nalexander

When using artifact builds, one can use the MOZ_ARTIFACT_REVISION
environment variable to force download artifacts from the given
revision.

When the VCS is git, it expects the revision to be a git ref or commit
sha1, which is resolved to a mercurial changeset via git-cinnabar.

It can however be convenient to just point to a given mercurial revision
directly, from, say, try, without pulling it first. This can actually be
useful even when the VCS is mercurial.

So if the given revision doesn't resolve to an existing git or hg commit,
and it's a complete 40-character sha1, we assume it's a valid mercurial
changeset.

Differential Revision: https://phabricator.services.mozilla.com/D11266

--HG--
extra : moz-landing-system : lando

python/mozbuild/mozbuild/artifacts.py

@@ -1247,18 +1247,34 @@ class Artifacts(object):
         return self._install_from_hg_pushheads(hg_pushheads, distdir)
 
     def install_from_revset(self, revset, distdir):
-        if self._hg:
-            revision = subprocess.check_output([self._hg, 'log', '--template', '{node}\n',
-                                                '-r', revset], cwd=self._topsrcdir).strip()
-            if len(revision.split('\n')) != 1:
-                raise ValueError('hg revision specification must resolve to exactly one commit')
-        else:
-            revision = subprocess.check_output([self._git, 'rev-parse', revset], cwd=self._topsrcdir).strip()
-            revision = subprocess.check_output([self._git, 'cinnabar', 'git2hg', revision], cwd=self._topsrcdir).strip()
-            if len(revision.split('\n')) != 1:
-                raise ValueError('hg revision specification must resolve to exactly one commit')
-            if revision == "0" * 40:
-                raise ValueError('git revision specification must resolve to a commit known to hg')
+        revision = None
+        try:
+            if self._hg:
+                revision = subprocess.check_output([self._hg, 'log', '--template', '{node}\n',
+                                                  '-r', revset], cwd=self._topsrcdir).strip()
+            elif self._git:
+                revset = subprocess.check_output([
+                    self._git, 'rev-parse', '%s^{commit}' % revset],
+                    stderr=open(os.devnull, 'w'), cwd=self._topsrcdir).strip()
+            else:
+                # Fallback to the exception handling case from both hg and git
+                raise subprocess.CalledProcessError()
+        except subprocess.CalledProcessError:
+            # If the mercurial of git commands above failed, it means the given
+            # revset is not known locally to the VCS. But if the revset looks
+            # like a complete sha1, assume it is a mercurial sha1 that hasn't
+            # been pulled, and use that.
+            if re.match(r'^[A-Fa-f0-9]{40}$', revset):
+                revision = revset
+
+        if revision is None and self._git:
+            revision = subprocess.check_output(
+                [self._git, 'cinnabar', 'git2hg', revset], cwd=self._topsrcdir).strip()
+
+        if revision == "0" * 40 or revision is None:
+            raise ValueError('revision specification must resolve to a commit known to hg')
+        if len(revision.split('\n')) != 1:
+            raise ValueError('revision specification must resolve to exactly one commit')
 
         self.log(logging.INFO, 'artifact',
                  {'revset': revset,