Issue 1777 - ensure_dependencies.py fails to detect unknown Git revisions

ensure_dependencies.py

 #!/usr/bin/env python
 # coding: utf-8
 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import sys
 import os
 import posixpath
@@ skipping 71 matching lines @@
   def istype(self, repodir):
     return os.path.exists(os.path.join(repodir, ".git"))
 
   def clone(self, source, target):
     source = source.rstrip("/")
     if not source.endswith(".git"):
       source += ".git"
     subprocess.check_call(["git", "clone", "--quiet", source, target])
 
   def get_revision_id(self, repo, rev="HEAD"):
-    command = ["git", "rev-parse", "--revs-only", rev]
-    return subprocess.check_output(command, cwd=repo).strip()
+    command = ["git", "rev-list", "--remotes=*", "--max-count=1", rev]

[Wladimir Palant, 2015/01/11 23:10:22]

Note that I don't really know how to use Git, and its command line interface is
quite a mess. So far that's the only command I found that will resolve tags into
revision IDs, keep existing revision IDs unchanged and complain about
non-existing ones.

[Wladimir Palant, 2015/01/11 23:39:28]

I noticed that the rev-list with --remotes specified will resolve HEAD
incorrectly (remote HEAD taken). On the other hand, without --remotes it will
refuse to work on fetched revisions above HEAD. It seems however that rev-parse
will produce the desired results if type is specified explicitly:
<rev>^{commit}. So I went with this solution now.

+    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=repo)
+
+    # Ignore stderr output and return code here: if revision lookup failed we
+    # should simply return an empty string.
+    result = process.communicate()[0]
+    return result.strip()
 
   def pull(self, repo):
     subprocess.check_call(["git", "fetch", "--quiet", "--all", "--tags"], cwd=repo)
 
   def update(self, repo, rev):
     subprocess.check_call(["git", "checkout", "--quiet", rev], cwd=repo)
 
   def ignore(self, target, repo):
     module = os.path.relpath(target, repo)
     exclude_file = os.path.join(repo, ".git", "info", "exclude")
@@ skipping 172 matching lines @@
       for l in file_content:
         print >>f, l
 
 if __name__ == "__main__":
   logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO)
   repos = sys.argv[1:]
   if not len(repos):
     repos = [os.getcwd()]
   for repo in repos:
     resolve_deps(repo)