.bin/git-rb-catchup

   1 #!/usr/bin/env python3
   2
   3 """Helper to automatically rebase onto latest commit possible."""
   4
   5 import argparse
   6 import subprocess
   7 import sys
   8
   9
  10 def git(args, **kwargs):
  11     """Run git."""
  12     kwargs.setdefault('check', True)
  13     kwargs.setdefault('capture_output', True)
  14     kwargs.setdefault('encoding', 'utf-8')
  15     return subprocess.run(['git'] + args, **kwargs)
  16
  17
  18 def rebase(target):
  19     """Try to rebase onto |target|."""
  20     try:
  21         git(['rebase', target])
  22         return True
  23     except KeyboardInterrupt:
  24         git(['rebase', '--abort'])
  25         print('aborted')
  26         sys.exit(1)
  27     except:
  28         git(['rebase', '--abort'])
  29         return False
  30
  31
  32 def rebase_bisect(lbranch, rbranch, behind):
  33     """Try to rebase branch as close to |rbranch| as possible."""
  34     def attempt(pos):
  35         target = f'{rbranch}~{pos}'
  36         print(f'Rebasing onto {target} ', end='', flush=True)
  37         print('.', end='', flush=True)
  38 #        git(['checkout', '-f', target])
  39         print('.', end='', flush=True)
  40 #        git(['checkout', '-f', lbranch])
  41         print('. ', end='', flush=True)
  42         ret = rebase(target)
  43         print('OK' if ret else 'failed')
  44         return ret
  45
  46     #"min" is the latest branch commit while "max" is where we're now.
  47     min = 0
  48     max = behind
  49     old_mid = None
  50     while True:
  51         mid = min + (max - min) // 2
  52         if mid == old_mid or mid < min or mid >= max:
  53             break
  54         if attempt(mid):
  55             max = mid
  56         else:
  57             min = mid
  58         old_mid = mid
  59     print('Done')
  60
  61
  62 def get_ahead_behind(lbranch, rbranch):
  63     """Return number of commits |lbranch| is ahead & behind relative to |rbranch|."""
  64     output = git(['rev-list', '--left-right', '--count', f'{lbranch}...{rbranch}']).stdout
  65     return [int(x) for x in output.split()]
  66
  67
  68 def get_tracking_branch(branch):
  69     """Return remote branch that |branch| is tracking."""
  70     merge = git(['config', '--local', f'branch.{branch}.merge']).stdout.strip()
  71     if not merge:
  72         return None
  73
  74     remote = git(['config', '--local', f'branch.{branch}.remote']).stdout.strip()
  75     if remote:
  76         if merge.startswith('refs/heads/'):
  77             merge = merge[11:]
  78         return f'{remote}/{merge}'
  79     else:
  80         return merge
  81
  82
  83 def get_local_branch():
  84     """Return the name of the local checked out branch."""
  85     return git(['branch', '--show-current']).stdout.strip()
  86
  87
  88 def get_parser():
  89     """Get CLI parser."""
  90     parser = argparse.ArgumentParser(description=__doc__)
  91     parser.add_argument(
  92         '--skip-initial-rebase-latest', dest='initial_rebase',
  93         action='store_false', default=True,
  94         help='skip initial rebase attempt onto the latest branch')
  95     parser.add_argument(
  96         'branch', nargs='?',
  97         help='branch to rebase onto')
  98     return parser
  99
 100
 101 def main(argv):
 102     """The main entry point for scripts."""
 103     parser = get_parser()
 104     opts = parser.parse_args(argv)
 105
 106     lbranch = get_local_branch()
 107     print(f'Local branch resolved to "{lbranch}"')
 108     if not lbranch:
 109         print('Unable to resolve local branch', file=sys.stderr)
 110         return 1
 111
 112     if opts.branch:
 113         rbranch = opts.branch
 114     else:
 115         rbranch = get_tracking_branch(lbranch)
 116     print(f'Remote branch resolved to "{rbranch}"')
 117
 118     ahead, behind = get_ahead_behind(lbranch, rbranch)
 119     print(f'Branch is {ahead} commits ahead and {behind} commits behind')
 120
 121     if not behind:
 122         print('Up-to-date!')
 123     elif not ahead:
 124         print('Fast forwarding ...')
 125         git(['merge'])
 126     else:
 127         if opts.initial_rebase:
 128             print(f'Trying to rebase onto latest {rbranch} ... ', end='', flush=True)
 129             if rebase(rbranch):
 130                 print('OK!')
 131                 return 0
 132             print('failed; falling back to bisect')
 133         rebase_bisect(lbranch, rbranch, behind)
 134
 135
 136 if __name__ == '__main__':
 137     sys.exit(main(sys.argv[1:]))