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Differential D6169

unshelve: disable unshelve during merge (issue5123)
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Authored by navaneeth.suresh on Mar 25 2019, 3:17 AM.

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rHG03f6480bfdda: unshelve: disable unshelve during merge (issue5123)
Summary

As stated in the issue5123, unshelve can destroy the second parent of
the context when tried to unshelve with an uncommitted merge. This
patch makes unshelve to abort when called with an uncommitted merge.

See how shelve.mergefiles works. Commit structure looks like this:

... -> pctx -> tmpwctx -> shelvectx
                  /
                 /
        second
        merge parent

pctx = parent before merging working context(first merge parent)
tmpwctx = commited working directory after merge(with two parents)
shelvectx = shelved context

shelve.mergefiles first updates to pctx then it reverts shelvectx to pctx with:

cmdutil.revert(ui, repo, shelvectx, repo.dirstate.parents(),
                       *pathtofiles(repo, files),
                       **{'no_backup': True})

Reverting tmpwctx files that were merged from second parent to pctx makes them
added because they are not in pctx.

Changing this revert operation is crucial to restore parents after unshelve. This is a
complicated issue as this is not fixing a regression. Thus, for the time being,
unshelve during an uncommitted merge can be aborted.

(Details taken from http://mercurial.808500.n3.nabble.com/PATCH-V3-shelve-restore-parents-after-unshelve-issue5123-tt4036858.html#a4037408)

Diff Detail

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rHG Mercurial
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Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

yuja added a subscriber: yuja.Mar 25 2019, 6:29 PM
As stated in the issue5123, unshelve can destroy the second parent of
the context when tried to unshelve with an uncommitted merge. This
patch makes unshelve to abort when called with an uncommitted merge.

Is it difficult to fix unshelve to not lose merge parents?

https://bz.mercurial-scm.org/show_bug.cgi?id=5123#c2

navaneeth.suresh added a comment.Mar 26 2019, 2:11 PM

Is it difficult to fix unshelve to not lose merge parents?
https://bz.mercurial-scm.org/show_bug.cgi?id=5123#c2

I'll try to come up with a fix. But, hg shelve is aborting during a merge. Can unshelve be aborted too? I don't have a strong opinion on this. I am just asking.

yuja added a comment.Mar 27 2019, 6:35 PM
> Is it difficult to fix unshelve to not lose merge parents?
> 
> https://bz.mercurial-scm.org/show_bug.cgi?id=5123#c2
I'll try to come up with a fix. But, `hg shelve` is aborting during a merge. Can `unshelve` be aborted too?

It could abort, but mpm said there would be no reason to, and I agree with
that. Unshelving on top of a merge seems somewhat useful.

yuja added a comment.Apr 1 2019, 7:04 PM
I saw some patches[0][1][2] trying to fix this issue. It seems like it's difficult to preserve the second parent.
[0]: http://mercurial.808500.n3.nabble.com/PATCH-shelve-adds-restoring-original-parents-after-unshelve-issue5123-tc4035657.html#none
[1]: http://mercurial.808500.n3.nabble.com/PATCH-V2-shelve-restore-parents-after-unshelve-issue5123-tc4036093.html#a4037370
[2]: http://mercurial.808500.n3.nabble.com/PATCH-V3-shelve-restore-parents-after-unshelve-issue5123-tt4036858.html#a4037408

Okay, let's disable unshelve then. Can you update the commit message to
include why we can't simply allow it?

navaneeth.suresh edited the summary of this revision. (Show Details)Apr 2 2019, 9:06 AM
navaneeth.suresh updated this revision to Diff 14616.
Closed by commit rHG03f6480bfdda: unshelve: disable unshelve during merge (issue5123) (authored by navaneeth.suresh). · Explain WhyApr 2 2019, 6:40 PM
This revision was automatically updated to reflect the committed changes.
navaneeth.suresh added a comment.Apr 2 2019, 11:48 PM

Thanks for queuing Yuya.

Revision Contents
Changeset List

PathPackages
Mhgext/shelve.py (6 lines)
Mtests/test-shelve.t (46 lines)

Diff 14635

hgext/shelve.py

return return
if abortf: if abortf:
return unshelveabort(ui, repo, state, opts) return unshelveabort(ui, repo, state, opts)
elif continuef: elif continuef:
return unshelvecontinue(ui, repo, state, opts) return unshelvecontinue(ui, repo, state, opts)
elif len(shelved) > 1: elif len(shelved) > 1:
raise error.Abort(_('can only unshelve one change at a time')) raise error.Abort(_('can only unshelve one change at a time'))
# abort unshelve while merging (issue5123)
parents = repo[None].parents()
if len(parents) > 1:
raise error.Abort(_('cannot unshelve while merging'))
elif not shelved: elif not shelved:
shelved = listshelves(repo) shelved = listshelves(repo)
if not shelved: if not shelved:
raise error.Abort(_('no shelved changes to apply!')) raise error.Abort(_('no shelved changes to apply!'))
basename = util.split(shelved[0][1])[1] basename = util.split(shelved[0][1])[1]
ui.status(_("unshelving change '%s'\n") % basename) ui.status(_("unshelving change '%s'\n") % basename)
else: else:
basename = shelved[0] basename = shelved[0]

tests/test-shelve.t

$ hg unshelve $ hg unshelve
unshelving change 'foo' unshelving change 'foo'
$ hg bookmarks $ hg bookmarks
\* foo (5|19):703117a2acfb (re) \* foo (5|19):703117a2acfb (re)
test (4|13):33f7f61e6c5e (re) test (4|13):33f7f61e6c5e (re)
$ cd .. $ cd ..
Abort unshelve while merging (issue5123)
----------------------------------------
$ hg init issue5123
$ cd issue5123
$ echo > a
$ hg ci -Am a
adding a
$ hg co null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo > b
$ hg ci -Am b
adding b
created new head
$ echo > c
$ hg add c
$ hg shelve
shelved as default
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg co 1
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg merge 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
-- successful merge with two parents
$ hg log -G
@ changeset: 1:406bf70c274f
tag: tip
parent: -1:000000000000
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: b
@ changeset: 0:ada8c9eb8252
user: test
date: Thu Jan 01 00:00:00 1970 +0000
summary: a
-- trying to pull in the shelve bits
-- unshelve should abort otherwise, it'll eat my second parent.
$ hg unshelve
abort: cannot unshelve while merging
[255]
$ cd ..