[StGIT PATCH] Fix popping on non-active branches

["Karl Hasselström" <kha@treskal.com>]

Resetting HEAD on the current branch when popping a patch on another
branch isn't a great idea.

Signed-off-by: Karl Hasselström <kha@treskal.com>
---

 stgit/git.py   |    8 ++++++--
 stgit/stack.py |   13 +++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/stgit/git.py b/stgit/git.py
index d7eb48e..837f927 100644
--- a/stgit/git.py
+++ b/stgit/git.py
@@ -298,14 +298,18 @@ def set_head_file(ref):
              [os.path.join('refs', 'heads', ref)]) != 0:
         raise GitException, 'Could not set head to "%s"' % ref
 
+def set_branch(branch, val):
+    """Point branch at a new commit object."""
+    if __run('git-update-ref', [branch, val]) != 0:
+        raise GitException, 'Could not update %s to "%s".' % (branch, val)
+
 def __set_head(val):
     """Sets the HEAD value
     """
     global __head
 
     if not __head or __head != val:
-        if __run('git-update-ref HEAD', [val]) != 0:
-            raise GitException, 'Could not update HEAD to "%s".' % val
+        set_branch('HEAD', val)
         __head = val
 
     # only allow SHA1 hashes
diff --git a/stgit/stack.py b/stgit/stack.py
index 3e9fc4f..76704e8 100644
--- a/stgit/stack.py
+++ b/stgit/stack.py
@@ -1063,12 +1063,13 @@ class Series(StgitObject):
 
         patch = Patch(name, self.__patch_dir, self.__refs_dir)
 
-        # only keep the local changes
-        if keep and not git.apply_diff(git.get_head(), patch.get_bottom()):
-            raise StackException, \
-                  'Failed to pop patches while preserving the local changes'
-
-        git.switch(patch.get_bottom(), keep)
+        if git.get_head_file() == self.get_branch():
+            if keep and not git.apply_diff(git.get_head(), patch.get_bottom()):
+                raise StackException(
+                    'Failed to pop patches while preserving the local changes')
+            git.switch(patch.get_bottom(), keep)
+        else:
+            git.set_branch(self.get_branch(), patch.get_bottom())
 
         # save the new applied list
         idx = applied.index(name) + 1