A simple script to automate shell history file merges.

historymerge

#!/usr/bin/env python

import sys

"""
historymerge: Merges a shell history file.

If you keep your shell history files in your hg repo, this script can be
useful for merging changes from various machines. Obviously you should
*never* check such things into public repos. This is for private repos
only (keep them on Dropbox or a code hoster that allows private repos -
and use two-factor auth or ssh keys to access).

To use this, add the following to your ~/.hgrc:

  [merge-tools]
  historymerge.priority = 100
  historymerge.executable = ~/bin/historymerge
  historymerge.args = $local $other $output

  [merge-patterns]
  .bash_history = historymerge

and then place this script in ~/bin/historymerge
"""

local_file = open(sys.argv[1], 'r')
other_file = open(sys.argv[2], 'r')
output_file = open(sys.argv[3], 'w')

local_iter = iter(local_file)
other_iter = iter(other_file)
try:
  for local_line in local_iter:
    # This can cause a StopIteration
    other_line = other_iter.next()
    if local_line == other_line:
      # Both files are the same here, print the line and move to next.
      output_file.write(other_line)
    else:
      # The files have diverged. Print other_file lines until one matches
      # the next local_file line.
      output_file.write(local_line)
      output_file.write(other_line)
      # This can cause a StopIteration
      local_line = local_iter.next()
      for other_line in other_iter:
        if local_line == other_line:
          output_file.write(local_line)
          break
        else:
          output_file.write(other_line)
      output_file.write(local_line)
except StopIteration:
  # One of the files is exhausted. Exit loop.
  pass

# One of the files might still have lines. Try and print from both of them.
for other_line in other_iter:
  output_file.write(other_line)
for local_line in local_iter:
  output_file.write(local_line)