Question

I have a platform neutral mercurial code repo called “Simulator”

and want to apply patches that target specific platform’s optimizations before a build.

According to the guide we can accomplish this by the use of patches with guards.

• Windows Experimental.patch +windows
• Unix Experimental.patch +unix
• Mac Experimental.patch +mac

However its starting to get cumbersome because our patch queue contains 100+ patches named like windows-memory-optimization.patch +windows, unix-memory-optimization.patch +unix, windows-io-experimental-bug-fix.patch +windows, etc etc. We organized it as groups in the series file, but the file is getting huge and using qseries / qapplied is getting unmanageable

Instead we would like to have a queue for windows, unix and mac.

So that patches can be organized as:

• Windows Patch Stack: memory-opt.patch, io-opt.patch, etc
• Unix Patch Stack: disk.patch, graphics.patch, etc
• Mac Patch Stack: io-fix.patch, io-opt.patch, experimental.patch, etc

Then swap the patch stacks for each platform in and out of the simulator repo. So that I can work on the windows patch stack and pop/push various subsystem optimization patches and work on them independently of the unix or mac patch stacks.

It does not look like I can do that, other than making 3 different repos specific to the each platform and maintaining the patch stacks that way.

Is there a way to, other than manually copying the .hg/patches directory in and out of the repo, to accomplish “swapping” patch stacks?

Answer 1

Interesting use of Mercurial Queues 🙂

I assume here that you are already versioning your mercurial queues somewhere. If you don’t/for those that don’t know how to do this, have a look at the relevant section from the hgbook: it’s a great way to collaborate/save incrementally your work without applying the patches.

Three named branches

It should be possible to maintain three different named branches, one for each platform, in your MQ repository.

To switch platform, just switch the active branch.

(with alias mq='hg -R $(hg root)/.hg/patches')

First create a windows branch:

$ mq branch windows
marked working directory as branch windows

created, but not yet committed.

Do some stuff, add patches:

$ hg qnew windowspatch
... do some stuff

Refresh, pop and commit:

$ hg qref
$ hg qpop -a
$ mq ci -m 'new windows branch'

You now have the default branch and the new windows branch:

$ mq branches
windows                       65:5fd4ef0b96c9
default                       64:06c1a56a3c08 (inactive)

Now create an Unix branch.

First switch back to the base default branch:

$ mq up default
1 files updated, 0 files merged, 1 files removed, 0 files unresolved

Create a new unix branch and add a unix-specific patch:

$ mq branch unix
marked working directory as branch unix
$ hg qnew unixpatch
... blahblah
$ hg qref
$ hg qpop -a
$ mq ci -m 'adding unix branch'
$ mq branches
unix                          66:c51bb2c7b413
windows                       65:5fd4ef0b96c9
default                       64:06c1a56a3c08 (inactive)

Usage

Don’t forget to qpop -a before operating on the mq repos…

Push all the windows patches

$ mq up windows
xx files updated, yy files merged, zz files removed, ww files unresolved
$ hg qpush -a

Three physical repos

Maintaining three separate (mercurial queue) branches can look a bit scary. If so, you can just use three different MQ repositories: one for each platform, each of them versioned in a different place.

For example :

$ cd mqs
$ hg qclone mq-windows windows
$ hg qclone mq-unix unix
$ hg qclone mq-mac mac

To work on different platforms, just switch folders (repos). The concept is similar to the first approach. But instead of having three internal branches in one MQ repo, you use three separate MQ repos.