Add 'git mrb' tool for 'git merge remote branch'.

It's a little utility I wrote that makes it super quick to merge
remote branches from remotes you're already tracking locally.

tools/git-mrb

@@ -0,0 +1,80 b''
+#!/usr/bin/env python
+"""git-mrb: merge remote branch.
+
+git mrb [remote:branch OR remote-branch] [onto] [upstream]
+
+remote must be locally available, and branch must exist in that remote.
+
+If 'onto' branch isn't given, default is 'master'.
+
+If 'upstream' repository isn't given, default is 'origin'.
+
+You can separate the remote and branch spec with either a : or a -.
+"""
+#-----------------------------------------------------------------------------
+# Imports
+#-----------------------------------------------------------------------------
+
+from subprocess import check_call
+import sys
+
+#-----------------------------------------------------------------------------
+# Functions
+#-----------------------------------------------------------------------------
+
+def sh(cmd):
+    cmd = cmd.format(**shvars)
+    print '$', cmd
+    check_call(cmd, shell=True)
+
+#-----------------------------------------------------------------------------
+# Main Script
+#-----------------------------------------------------------------------------
+
+argv = sys.argv[1:]
+narg = len(argv)
+
+try:
+    branch_spec = argv[0]
+    sep = ':' if ':' in branch_spec else '-'
+    remote, branch = branch_spec.split(':', 1)
+    if not branch:
+        raise ValueError('Branch spec %s invalid, branch not found' %
+                         branch_spec)
+except:
+    import traceback as tb
+    tb.print_exc()
+    print __doc__
+    sys.exit(1)
+
+onto = argv[1] if narg >= 2 else 'master'
+upstream = argv[1] if narg == 3 else 'origin'
+
+# Git doesn't like ':' in branch names.
+if sep == ':':
+    branch_spec = branch_spec.replace(':', '-')
+
+# Global used by sh
+shvars = dict(remote=remote, branch_spec=branch_spec, branch=branch,
+              onto=onto, upstream=upstream)
+
+# Start git calls.
+sh('git fetch {remote}')
+sh('git checkout -b {branch_spec} {onto}')
+sh('git merge {remote}/{branch}')
+
+print """
+*************************************************************
+ Run test suite.  If tests pass, run the following to merge:
+
+git checkout {onto}
+git merge {branch_spec}
+git push {upstream} {onto}
+
+*************************************************************
+""".format(**shvars)
+
+ans = raw_input("Revert to master and delete temporary branch? [y/N]: ")
+if ans.lower() in ('y', 'yes'):
+    sh('git checkout {onto}')
+    sh('git branch -D {branch_spec}')