Easy branch-landing of patches

December 2nd, 2009

I often find myself landing patches on our 1.9.2 and 1.9.1 branches, both of which are in Mercurial repositories. This generally involves getting a changeset from the mozilla-central repository into one of these repositories, and also amending the changeset message to include the name of the person who gave me approval to land. There was some discussion recently on how it’s kind of a pain to do that. I’ve cooked up an easy solution for my own needs, perhaps it will serve yours as well.

I use “hg transplant” to get changesets from one repository to another. This assumes that you have local clones of both the source repository (mozilla-central in this case) and the destination repository (mozilla-1.9.2 or 1.9.1, usually). Assuming you had both clones side-by-side in a directory, you could run the transplant command in the destination repository’s working directory like so (where xxx is the changeset identifier of the changeset you want transplanted, you can also specify more than one changeset):

hg transplant -s ../mozilla-central xxx

The transplant command conveniently includes a “–filter” option that will let you alter the commit message or patch while transplanting. This requires you to have some sort of script for transplant to run. Here’s what I’m using (on Linux):


if test -n "$APPEND"; then
 echo " $APPEND" >> "$1";
 if test -n "$EDITOR"; then
 $EDITOR "$1";
 editor "$1";

Save this as “transplant.sh” somewhere (and ensure that it’s executable), then in your ~/.hgrc, add a section:

filter = /path/to/transplant.sh

Now, when you run “hg transplant”, by default it will open an editor to edit the commit message for each changeset, allowing you to add approval information. But, even better, transplant.sh will append the contents of the “APPEND” variable if set, so you can run transplant like so to quickly append approval information:

APPEND="a=someone" hg transplant -s ../mozilla-central xxx

I find that this saves me a bunch of time, so hopefully it’s useful to someone else!

4 Responses to “Easy branch-landing of patches”

  1. Tro Says:

    You’re right!

  2. Ehsan Akhgari Says:

    Thanks a lot for sharing this, Ted! I already knew about hg transplant, but didn’t know about the filter trick, which prevented me from using it, but now I have another handy tool to deal with our branches in hg, which is awesome!

  3. Neil Rashbrook Says:

    “${EDITOR:=editor}” “$1”

  4. tmielczarek Says:

    Yes, my shell-scripting is weak. 🙂