Converting SVN Commits to Git Patches

In case you find yourself in need of a way to turn an svn revision into a git patch that can be applied with ‘git am’, keeping the commit message and authorship information, here’s a script I used recently:
#!/usr/bin/python  
#  
# svnrev2git.py - Convert an SVN revsion to a Git patch.  
#  
# Author: James Bowes <jbowes@repl.ca>  
#  
# Usage:  
#   $> cd my-svn-repo  
#   $> python svnrev2git.py [AUTHORS_FILE] [REV_RANGE | REVSION [REVISION..]]  
#  
#   AUTHORS_FILE - a CSV of  svn username, full name, email  
#   REV_RANGE - an svn revision range, like 100-700  
#   REVISION - a single svn revision  
#  
#   You may specify either a revision range, or a series of individual  
#   svn revisions  
#  
# Output:  
#   A series of git style patch files, one per svn revision, which can then be  
#   applied with 'git am'  
#  
# Why use this instead of 'git svn'?  
#   I had done a large repo conversion via git svn where we wanted no downtime  
#   for the switchover. After removing the git svn specific info from our git  
#   commits, I used this tool to bring in commits from svn, keeping svn and git  
#   in sync, until we were ready to switch.  

import sys  
import commands  

def svnlog_to_gitlog(authors, svnlog):  

    lines = svnlog.split("\n")  
    lines = lines[1:-1]  

    metainfo = lines[0].split(" | ")  
    subject = lines[2]  
    description = lines[3:]  

    author = metainfo[1]  

    day = metainfo[2].split("(")[1][:-1]  
    time = metainfo[2].split(" ")[1]  
    offset = metainfo[2].split(" ")[2]  

    gitlog = []  
    gitlog += ["From: %s <%s>" % authors[author]]  
    gitlog += ["Date: %s %s %s" % (day, time, offset)]  
    gitlog += ["Subject: [PATCH] %s" % subject]  
    gitlog += [""]  
    gitlog += description  
    gitlog += [""]  

    return '\n'.join(gitlog)  

def svndiff_to_gitdiff(svndiff):  
    lines = svndiff.split("\n")  

    gitdiff = []  
    for line in lines:  
        if line.startswith("--- "):  
            gitdiff.append("--- a/" + line[4:])  
        elif line.startswith("+++ "):  
            gitdiff.append("+++ b/" + line[4:])  
        else:  
            gitdiff.append(line)  

    return '\n'.join(gitdiff)  

def make_patch(authors, rev):  
    out = commands.getoutput("svn log -c %s ." % rev)  

    if len(out.split("\n")) < 2:  
        print "skipping r%s" % rev  
        return  

    patch = open(rev + ".patch", 'w')  
    patch.write(svnlog_to_gitlog(authors, out))  
    patch.write("---\n\n")  

    out = commands.getoutput("svn diff -c %s ." % rev)  
    patch.write(svndiff_to_gitdiff(out))  

    patch.write("\n---\n")  
    patch.write("svnrev2git.py\n")  

    patch.close()  
    print "wrote %s.patch" % rev  

def main(args):  
    author_file = open(args[0])  
    authors = {}  

    print "loading authors"  
    for line in author_file.readlines():  
        parts = line.strip().split(", ")  
        authors[parts[0]] = (parts[1], parts[2])  

    author_file.close()  

    revs = args[1:]  

    if len(revs) == 1 and '-' in revs[0]:  
        start, end = revs[0].split('-')  
        start = int(start)  
        end = int(end)  
        revs = [str(x) for x in range(start, end + 1)]  

    for rev in revs:  
        make_patch(authors, rev)  

if __name__ == "__main__":  
    main(sys.argv[1:])
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