git-retext

#!/usr/bin/env python3

"""
Like git-rebase interactive, but instead of editing a script, you edit the
exported patches directly, which are presented in an email format.

You can edit the diff directly.  For allowing this, this relies on
`recountdiff` to fix diff hunk header numbers.  See `recountdiff` regarding the
editing of diffs.
"""

import sys
import os
import tempfile
import re
import subprocess

from optparse import OptionParser

def system(cmd):
    return os.system(cmd)

class Abort(Exception): pass

def e_system(cmd):
    r = system(cmd)
    if r != 0:
        raise Abort(f"command {cmd} failed: {r}");

C = re.compile("From ([a-f0-9]+) Mon Sep 17 00:00:00 2001")

def to_commits(content):
    commits = []
    githash = None
    lines = []
    for line in content.splitlines():
        match = C.match(line)
        if match:
            if lines:
                commits.append((githash, lines))
            lines = []
            githash = match.groups(0)[0]
        lines.append(line)
    if lines:
        commits.append((githash, lines))
    return commits

def error_msg(msg):
    print('\u001b[31m', end='', file=sys.stderr)
    print(msg, file=sys.stderr)
    print('\u001b[0m', end='', file=sys.stderr)
    sys.stderr.flush()

def main():
    parser = OptionParser()

    base = sys.argv[1]
    ret = os.system("git status --porcelain")
    if ret != 0:
        print("There are uncommited changes", file=sys.stderr)
        return

    original = os.popen(f"git rev-parse HEAD").read().strip()
    if original == "":
        print("Unable to retrive original revision", file=sys.stderr)
        return


    rc = subprocess.call(['which', 'recountdiff'])
    if rc != 0:
        print('recountdiff missing in path!', file=sys.stderr)
        return

    e_system(f"git rev-parse {base} > /dev/null")
    editor = os.popen("git config core.editor").read().strip()
    if not editor:
        editor = os.getenv("EDITOR", "vi")

    filename = tempfile.mktemp("git-retext.diff")

    pipe = os.popen(f"git format-patch --no-signature --stdout {base}..", "r")
    before_edit = pipe.read()

    fobj = open(filename, "w")
    fobj.write(before_edit)
    fobj.close()

    rcode = os.system(f"{editor} {filename}")
    success = False
    try:
        if rcode == 0:
            after_edit = open(filename, "r").read()
            new_data = []
            for (_, lines) in to_commits(after_edit):
                fobj = open(filename, "w")
                fobj.write("\n".join(lines))
                fobj.close()
                pipe = os.popen(f"recountdiff {filename}")
                fixed = pipe.read() + "\n"
                ret = pipe.close()
                if ret:
                    error_msg("recountdiff returned error")
                new_data.append(fixed)

            fobj = open(filename, "w")
            for data in new_data:
                fobj.write(data)
            fobj.close()

            e_system(f"git reset --hard {base}")
            e_system(f"git am < {filename}")
            success = True
    finally:
        os.unlink(filename)

        if not success:
            error_msg("Not successful, reverting to original")
            sys.stderr.flush()

            system(f"git am --abort")
            e_system(f"git reset --hard {original}")
            sys.exit(1)

if __name__ == "__main__":
    main()