[PATCH 08/14] [git] Try to find requested branch remotely if not available

[Dirk Wallenstein <halsmit t-online de>]

If a branch switch is requested but the branch is not available,
upstream will be fetched and the branch will be looked up again, before
failing.

This should make the branch switching independent of the concerns stated
in (GNOME bug 591470) and commit f7d5f81b6ca02ee5.

Signed-off-by: Dirk Wallenstein <halsmit t-online de>
---
 jhbuild/versioncontrol/git.py |   16 ++++++++++++++++
 1 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/jhbuild/versioncontrol/git.py b/jhbuild/versioncontrol/git.py
index cc616ff..fac7111 100644
--- a/jhbuild/versioncontrol/git.py
+++ b/jhbuild/versioncontrol/git.py
@@ -202,6 +202,17 @@ class GitBranch(Branch):
         except CommandError:
             return None
 
+    def _find_remote_branch_online_if_necessary(self, buildscript,
+            remote_name, branch_name):
+        """Try to find the given branch first, locally, then remotely, and state
+        the availability in the return value."""
+        wanted_ref = remote_name + '/' + branch_name
+        if self._execute_git_predicate( ['git', 'show-ref', wanted_ref]):
+            return True
+        buildscript.execute(['git', 'fetch'], cwd=self.get_checkoutdir(),
+                extra_env=get_git_extra_env())
+        return self._execute_git_predicate( ['git', 'show-ref', wanted_ref])
+
     def _switch_branch_if_necessary(self, buildscript):
         """
         The switch depends on the requested tag, the requested branch, and the
@@ -227,6 +238,11 @@ class GitBranch(Branch):
                 if self.local_branch_exist(wanted_branch, buildscript):
                     switch_command = ['git', 'checkout', wanted_branch]
                 else:
+                    if not self._find_remote_branch_online_if_necessary(
+                            buildscript, 'origin', wanted_branch):
+                        raise CommandError(_('The requested branch "%s" is '
+                                'not available. Neither locally, nor remotely '
+                                'in the origin remote.' % wanted_branch))
                     switch_command = ['git', 'checkout', '--track', '-b',
                             wanted_branch, 'origin/' + wanted_branch]
         if switch_command:
-- 
1.7.1