unsubmodule.py

#!/usr/bin/python2.6

# This script "unsubmodulizes" a git repository - i.e. it takes a git
# repository with submodules and replaces the submodules with the
# history of the submodule merged into a subdirectory of the same
# name.  I knocked this up quickly as an answer to this stackoverflow
# question:
#
#   http://stackoverflow.com/questions/4542729/undo-submodulization-in-git
#
# ... and so it hasn't been tested much: use entirely at your own
# risk, etc.  Afterwards, your git repository will have multiple root
# commits.

import datetime
import re
import sys
from subprocess import Popen, PIPE, check_call, call

# Exit unless the working tree matches the index and the index matches
# HEAD:

if 0 != call(["git","diff","--exit-code"]):
    print >> sys.stderr, "There are unstaged changes - git status should be clean"
    sys.exit(1)

if 0 != call(["git","diff","--cached","--exit-code"]):
    print >> sys.stderr, "There are changes staged but not committed - git status should be clean"
    sys.exit(1)

# Find the names of every submodule and the commit that the submodule
# should be at:

submodules = []

p = Popen(["git","ls-files","--error-unmatch","--stage"],stdout=PIPE)
output = p.communicate()[0]
if p.returncode != 0:
    raise Exception, "Finding the submodules failed"
for line in output.decode().splitlines(False):
    m = re.search('^160000 ([a-f0-9]{40}) \d+\s+(.*)$',line)
    if m:
        c, s = m.groups()
        if re.search('[:+]',s):
            # ':' or '+' in the submodule name will certainly cause
            # trouble when we create a remote name based on it, but
            # this isn't an exhaustive check (FIXME)
            raise Exception, "A remote name created from "+s+" is unlikely to be valid"
        submodules.append((s,c))

timestamp = datetime.datetime.now().strftime("%Y%m%d%H%M%S")

for submodule, commit in submodules:
    print "=== Doing", submodule
    # Create temporary names for the remote and branch, taking very
    # cursory steps to avoid collisions with existing branches /
    # remotes:
    remote_name = "submodule-"+submodule+"-"+timestamp
    branch_name = "tmp-"+submodule+"-"+timestamp
    # Find the URL of the submodule:
    p = Popen(["git","config","-f",".gitmodules","--get",'submodule.'+submodule+'.url'],stdout=PIPE)
    submodule_url = p.communicate()[0].decode().strip()
    if p.returncode != 0:
        raise Exception, "Getting the submodule URL failed"
    print "Got submodule:", submodule, "at commit", commit, "with URL", submodule_url
    # Add a remote for the submodule's URL:
    check_call(["git","remote","add",remote_name,submodule_url])
    # Fetch all the objects required for the submodule:
    check_call(["git","fetch",remote_name])
    # Create a temporary branch based on the committed submodule version:
    check_call(["git","branch",branch_name,commit])
    # Commit removal of the submodule:
    check_call(["git","rm","--cached",submodule])
    check_call(["git","commit","-m","Removed the submodule "+submodule])
    # Move the existing submodule out of the way:
    check_call(["mv",submodule,submodule+"."+timestamp])    
    # Merge in the branch to the subdirectory:
    check_call(["git","merge","-s","ours","--no-commit",branch_name])
    check_call(["git","read-tree","--prefix="+submodule,"-u",branch_name])
    check_call(["git","commit","-m","Merge in "+submodule+" as a subdirectory"])
    # Remove the branch and remote that the script created:
    check_call(["git","branch","-d",branch_name])
    check_call(["git","remote","rm",remote_name])
    # Finally, get the subdirectory from the index:
    check_call(["git","checkout","--",submodule])