.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, leave_rebase=False):
  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     # "pmin" is the latest branch position while "pmax" is where we're now.
  47     pmin = 0
  48     pmax = behind
  49     old_mid = None
  50     first_fail = 0
  51     while True:
  52         mid = pmin + (pmax - pmin) // 2
  53         if mid == old_mid or mid < pmin or mid >= pmax:
  54             break
  55         if attempt(mid):
  56             pmax = mid
  57         else:
  58             first_fail = max(first_fail, mid)
  59             pmin = mid
  60         old_mid = mid
  61
  62     if pmin or pmax:
  63         last_target = f'{rbranch}~{first_fail}'
  64         if leave_rebase:
  65             print('Restarting', last_target)
  66             result = git(['rebase', last_target], check=False)
  67             print(result.stdout.strip())
  68         else:
  69             print('Found first failure', last_target)
  70     else:
  71         print('All caught up!')
  72
  73
  74 def get_ahead_behind(lbranch, rbranch):
  75     """Return number of commits |lbranch| is ahead & behind relative to |rbranch|."""
  76     output = git(['rev-list', '--left-right', '--count', f'{lbranch}...{rbranch}']).stdout
  77     return [int(x) for x in output.split()]
  78
  79
  80 def get_tracking_branch(branch):
  81     """Return remote branch that |branch| is tracking."""
  82     merge = git(['config', '--local', f'branch.{branch}.merge']).stdout.strip()
  83     if not merge:
  84         return None
  85
  86     remote = git(['config', '--local', f'branch.{branch}.remote']).stdout.strip()
  87     if remote:
  88         if merge.startswith('refs/heads/'):
  89             merge = merge[11:]
  90         return f'{remote}/{merge}'
  91     else:
  92         return merge
  93
  94
  95 def get_local_branch():
  96     """Return the name of the local checked out branch."""
  97     return git(['branch', '--show-current']).stdout.strip()
  98
  99
 100 def get_parser():
 101     """Get CLI parser."""
 102     parser = argparse.ArgumentParser(description=__doc__)
 103     parser.add_argument(
 104         '--skip-initial-rebase-latest', dest='initial_rebase',
 105         action='store_false', default=True,
 106         help='skip initial rebase attempt onto the latest branch')
 107     parser.add_argument(
 108         '--leave-at-last-failed-rebase', dest='leave_rebase',
 109         action='store_true', default=False,
 110         help='leave tree state at last failing rebase')
 111     parser.add_argument(
 112         'branch', nargs='?',
 113         help='branch to rebase onto')
 114     return parser
 115
 116
 117 def main(argv):
 118     """The main entry point for scripts."""
 119     parser = get_parser()
 120     opts = parser.parse_args(argv)
 121
 122     lbranch = get_local_branch()
 123     print(f'Local branch resolved to "{lbranch}"')
 124     if not lbranch:
 125         print('Unable to resolve local branch', file=sys.stderr)
 126         return 1
 127
 128     if opts.branch:
 129         rbranch = opts.branch
 130     else:
 131         rbranch = get_tracking_branch(lbranch)
 132     print(f'Remote branch resolved to "{rbranch}"')
 133
 134     ahead, behind = get_ahead_behind(lbranch, rbranch)
 135     print(f'Branch is {ahead} commits ahead and {behind} commits behind')
 136
 137     if not behind:
 138         print('Up-to-date!')
 139     elif not ahead:
 140         print('Fast forwarding ...')
 141         git(['merge'])
 142     else:
 143         if opts.initial_rebase:
 144             print(f'Trying to rebase onto latest {rbranch} ... ', end='', flush=True)
 145             if rebase(rbranch):
 146                 print('OK!')
 147                 return 0
 148             print('failed; falling back to bisect')
 149         rebase_bisect(lbranch, rbranch, behind, leave_rebase=opts.leave_rebase)
 150
 151
 152 if __name__ == '__main__':
 153     sys.exit(main(sys.argv[1:]))