Hg: How to do a rebase like git's rebase

Question

Hey guys,

In Git I can do this:

1. Start working on new feature:
$ git co -b newfeature-123  # (a local feature development branch)
do a few commits (M, N, O)

master A---B---C
                \
newfeature-123   M---N---O

2. Pull new changes from upstream master:
$ git pull
(master updated with ff-commits)

master A---B---C---D---E---F
                \
newfeature-123   M---N---O

3. Rebase off master so that my new feature 
can be developed against the latest upstream changes:
(from newfeature-123)
$ git rebase master

master A---B---C---D---E---F
                            \
newfeature-123               M---N---O

I want to know how to do the same thing in Mercurial, and I've scoured the web for an answer, but the best I could find was this: http://www.selenic.com/pipermail/mercurial/2007-June/013393.html

That link provides 2 examples:
1. I'll admit that this: (replacing the revisions from the example with those from my own example)

hg up -C F  
hg branch -f newfeature-123  
hg transplant -a -b newfeature-123 

is not too bad, except that it leaves behind the pre-rebase M-N-O as an unmerged head and creates 3 new commits M',N',O' that represent them branching off the updated mainline.

Basically the problem is that I end up with this:

master A---B---C---D---E---F
                \           \
newfeature-123   \           M'---N'---O'
                  \
newfeature-123     M---N---O

this is not good because it leaves behind local, unwanted commits that should be dropped.

1. The other option from the same link is

hg qimport -r M:O
hg qpop -a
hg up F
hg branch newfeature-123
hg qpush -a
hg qdel -r qbase:qtip

and this does result in the desired graph:

master A---B---C---D---E---F
                            \
newfeature-123               M---N---O

but these commands (all 6 of them!) seem so much more complicated than

$ git rebase master

I want to know if this is the only equivalent in Hg or if there is some other way available that is simple like Git.

Thanks!!

Jamie

Answer 1

What is wrong with the Rebase Extension? (implemented as part of the SummerOfCode 2008)

In those cases it can be useful to "detach" the local changes, synchronize the repository with the mainstream and then append the private changes on top of the new remote changes. This operation is called rebase.

Getting from:

to:

Answer 2

Assuming you have a modern Hg installation, you can simply add:

[extensions]
rebase = 

to ~/.hgrc.

Then you can use the commands hg rebase, hg pull --rebase, or hg help rebase.

Answer 3

VonC has the answer you're looking for, the Rebase Extension. It is, however, worth spending a second or two thinking about why neither mq nor rebase are enabled by default in mercurial: because mercurial is all about indelible changesets. When I work in the manner you're describing, which is nearly daily, here's the pattern I take:

1. Start working on a new feature:
$ hg clone mainline-repo newfeature-123
do a few commits (M, N, O)

master A---B---C
                \
newfeature-123   M---N---O

2. Pull new changes from upstream mainline:
$ hg pull

master A---B---C---D---E---F
                \
newfeature-123   M---N---O

3. merge master into my clone so that my new feature 
can be developed against the latest upstream changes:
(from newfeature-123)
$ hg merge F

master A---B---C---D---E---F
                \           \
newfeature-123   M---N---O---P

and that's really all that's necessary. I end up with a newfeature-123 clone I can easily push back to the mainline when I'm happy with it. Most importantly, however, I never changed history. Someone can look at my csets and see what they were originally coded against and how I reacted to changes in the mainline throughout my work. Not everyone thinks that has value, but I'm a firm believer that it's the job of source control to show us not what we wished had happened, but what actually happened -- every deadend and every refactor should leave an indelible trace, and rebasing and other history editing techniques hide that.

Now go pick VonC's answer while I put my soapbox away. :)