Merge lp:~lazypower/charm-helpers/git-fetch-update into lp:charm-helpers

[Charles Butler]

This alters the behavior of the git fetcher by adding a small loop to attempt updating of a git repository if the path exists on disk prior to attempting a clone.

The existing behavior is to raise a UnhandledRepositoryUrl exception when the path exists, which is a bit confusing to consumers of install_remote with git VCS urls - which seems to be a one shot fetcher. Run once, and guard against subsequent runs.

If this would fundamentally change the behavior of install_remote, i do not +1 this merge, but wanted to start the conversation around this small patch to see if we can't update charm-helpers to be a little more VCS friendly for cheap operations like an update.

Unmerged revisions

441. By Charles Butler on 2015-09-04

Adds a small logic loop to attempt an update of an existing directory if the
directory exists, and the git handler has assumed control from install_remote.

=== modified file 'charmhelpers/fetch/giturl.py'
--- charmhelpers/fetch/giturl.py	2015-07-09 19:56:05 +0000
+++ charmhelpers/fetch/giturl.py	2015-09-04 03:48:06 +0000
@@ -27,10 +27,13 @@
 
 try:
     from git import Repo
+    from git.cmd import Git
 except ImportError:
     from charmhelpers.fetch import apt_install
     apt_install("python-git")
     from git import Repo
+    from git.cmd import Git
+
 
 from git.exc import GitCommandError  # noqa E402
 
@@ -62,6 +65,13 @@
         else:
             dest_dir = os.path.join(os.environ.get('CHARM_DIR'), "fetched",
                                     branch_name)
+        if os.path.exists(dest_dir):
+            # install_from when using git remotes should default to
+            # updating the repository on a subsequent run.
+            g = Git(dest_dir)
+            g.pull()
+            return dest_dir
+
         if not os.path.exists(dest_dir):
             mkdir(dest_dir, perms=0o755)
         try: