ui: add special-purpose atexit functionality
In spite of its longstanding use, Python's built-in atexit code is
not suitable for Mercurial's purposes, for several reasons:
* Handlers run after application code has finished.
* Because of this, the code that runs handlers swallows exceptions
(since there's no possible stacktrace to associate errors with).
If we're lucky, we'll get something spat out to stderr (if stderr
still works), which of course isn't any use in a big deployment
where it's important that exceptions get logged and aggregated.
* Mercurial's current atexit handlers make unfortunate assumptions
about process state (specifically stdio) that, coupled with the
above problems, make it impossible to deal with certain categories
of error (try "hg status > /dev/full" on a Linux box).
* In Python 3, the atexit implementation is completely hidden, so
we can't hijack the platform's atexit code to run handlers at a
time of our choosing.
As a result, here's a perfectly cromulent atexit-like implementation
over which we have control. This lets us decide exactly when the
handlers run (after each request has completed), and control what
the process state is when that occurs (and afterwards).
$ cat <<EOF >> $HGRCPATH
> [extensions]
> convert =
> [convert]
> hg.tagsbranch = 0
> EOF
$ hg init source
$ cd source
$ echo a > a
$ hg ci -qAm adda
Add a merge with one parent in the same branch
$ echo a >> a
$ hg ci -qAm changea
$ hg up -qC 0
$ hg branch branch0
marked working directory as branch branch0
(branches are permanent and global, did you want a bookmark?)
$ echo b > b
$ hg ci -qAm addb
$ hg up -qC
$ hg merge default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -qm mergeab
$ hg tag -ql mergeab
$ cd ..
Miss perl... sometimes
$ cat > filter.py <<EOF
> import sys, re
>
> r = re.compile(r'^(?:\d+|pulling from)')
> sys.stdout.writelines([l for l in sys.stdin if r.search(l)])
> EOF
convert
$ hg convert -v --config convert.hg.clonebranches=1 source dest |
> python filter.py
3 adda
2 changea
1 addb
pulling from default into branch0
1 changesets found
0 mergeab
pulling from default into branch0
1 changesets found
Add a merge with both parents and child in different branches
$ cd source
$ hg branch branch1
marked working directory as branch branch1
$ echo a > file1
$ hg ci -qAm c1
$ hg up -qC mergeab
$ hg branch branch2
marked working directory as branch branch2
$ echo a > file2
$ hg ci -qAm c2
$ hg merge branch1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg branch branch3
marked working directory as branch branch3
$ hg ci -qAm c3
$ cd ..
incremental conversion
$ hg convert -v --config convert.hg.clonebranches=1 source dest |
> python filter.py
2 c1
pulling from branch0 into branch1
4 changesets found
1 c2
pulling from branch0 into branch2
4 changesets found
0 c3
pulling from branch1 into branch3
5 changesets found
pulling from branch2 into branch3
1 changesets found