Fix error syncing to LKGR due to misparsing of Cygwin git-svn output.

BUG=138104
TEST=


Review URL: https://chromiumcodereview.appspot.com/10826035

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@150952 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/scm.py b/scm.py
index aade53e..e99acc0 100644
--- a/scm.py
+++ b/scm.py
@@ -391,14 +391,19 @@
       return None
 
   @staticmethod
+  def ParseGitSvnSha1(output):
+    """Parses git-svn output for the first sha1."""
+    match = re.search(r'[0-9a-fA-F]{40}', output)
+    return match.group(0) if match else None
+
+  @staticmethod
   def GetSha1ForSvnRev(cwd, rev):
     """Returns a corresponding git sha1 for a SVN revision."""
     if not GIT.IsGitSvn(cwd=cwd):
       return None
     try:
-      lines = GIT.Capture(
-          ['svn', 'find-rev', 'r' + str(rev)], cwd=cwd).splitlines()
-      return lines[-1].strip() if lines else None
+      output = GIT.Capture(['svn', 'find-rev', 'r' + str(rev)], cwd=cwd)
+      return GIT.ParseGitSvnSha1(output)
     except subprocess2.CalledProcessError:
       return None