Renaming a Mercurial branch with the evolve extension

Short version (rename from $OLD to $NEW):

ROOT="$(hg id -qr 'first(roots(branch('$OLD')))')"
MSG="$(hg log -r $ROOT -T '{desc}')"  

hg update $ROOT
hg branch $NEW
hg commit --amend -m "$MSG"
hg evolve --all

Mercurial records in which named branch a commit was created. This can be inconvenient when you choose temporary branch names like "foo" or "justworkdamnit".

The evolve extension [1] enables safe, collaborative history editing which removes this inconvenience while preserving the reliability guarantees of Mercurial [2].

Here I show in a quick example how to rename a branch in Mercurial using the evolve extension.

You can use this method for all changes which you did not transfer elsewhere yet (they must be in draft or secret phase [3]).

Note (2016): The evolve extension is still in testing. Do not use it for production yet. If you want to help stabilizing it, please join evolve-testers [4]. I’ve been using it for more than a year, but I know how to fix things when I hit a bug in the evolve extension.

Setup evolve

hg clone https://www.mercurial-scm.org/repo/evolve/ ~/.local/share/hgext-evolve
echo "[extensions]
evolve = ~/.local/share/hgext-evolve/hgext/evolve.py" >> ~/.hgrc

Rename a branch

create repo with wrong branch name

hg init foo
cd foo
echo 1 > 1
hg ci -Am 1
echo stable > 1
hg branch stapling
hg ci -m stable
# add a second commit to the branch
# to make this non-trivial
echo stable2 > 1
hg ci -m stable2

change the branch name

# amend the first revision in the branch
hg up -r "first(branch(stapling))"
hg branch stable
hg ci --amend -m stable
# (notes that there is an unstable changeset)
# evolve the history
hg evolve

and check that it’s correct

hg log -G

That’s it.

Result

@  changeset:   5:1822f3b02b72
|  branch:      stable
|  tag:         tip
|  user:        Freenet
|  date:        Fri Nov 18 00:56:57 2016 +0100
|  summary:     stable2
|
o  changeset:   4:d47764612e1a
|  branch:      stable
|  parent:      0:d2b5bb69b11b
|  user:        Freenet
|  date:        Fri Nov 18 00:56:56 2016 +0100
|  summary:     stable
|
o  changeset:   0:d2b5bb69b11b
   user:        Freenet
   date:        Fri Nov 18 00:56:55 2016 +0100
   summary:     1

☺ Yay! ☺

Happy Hacking!

PS: If you want to share this: Short on GNU social [5]

PPS: If you want to tweet this:

hg branch name O→N
I="$(hg id -qr 'first(branch('$O'))')"
M="$(hg log -r $I [6] -T' {desc}')"
hg up $I [6]
hg branch $N [7]
hg ci --amend -m "$M"
hg ev

— ((λ()'ArneBab)) (@ArneBab) November 18, 2016 [8]

PPPS: For efficient collaboration via Mercurial see the complete branching strategy [9].