comparison tests/test-shelve.t @ 25774:4f8c20fe66f0

shelve: keep old backups if timestamp can't decide exact order of them

Before this patch, backups to be discarded are decided by steps below
at 'hg unshelve' or so:

  1. list '(st_mtime, filename)' tuples of each backups up
  2. sort list of these tuples, and
  3. discard backups other than 'maxbackups' ones at the end of list

This doesn't work well in the case below:

  - "sort by name" order differs from actual backup-ing order, and
  - some of backups have same timestamp

For example, 'test-shelve.t' satisfies the former condition:

  - 'default-01' < 'default-1' in "sort by name" order
  - 'default-1'  < 'default-01' in actual backup-ing order

Then, 'default-01' is discarded instead of 'default-1' unexpectedly,
if they have same timestamp. This failure appears occasionally,
because the most important condition "same timestamp" is timing
critical.

To avoid such unexpected discarding, this patch keeps old backups if
timestamp can't decide exact order of them.

Timestamp of the border backup (= the oldest one of recent
'maxbackups' ones) as 'bordermtime' is used to examine whether
timestamp can decide exact order of backups.

25773:de654a83fe1c

  $ hg revert --all -q
  $ rm a/a.orig b.rename/b c.copy

apply it and make sure our state is as expected

  $ hg unshelve
  unshelving change 'default-01'
  $ hg status -C
  M a/a
  A b.rename/b
    b/b
  A c.copy
    c
  R b/b
  $ hg shelve -l

  $ hg unshelve
  abort: no shelved changes to apply!
  [255]
  $ hg unshelve foo

25774:4f8c20fe66f0

  $ hg revert --all -q
  $ rm a/a.orig b.rename/b c.copy

apply it and make sure our state is as expected

(this also tests that same timestamp prevents backups from being
removed, even though there are more than 'maxbackups' backups)

  $ f -t .hg/shelve-backup/default.hg
  .hg/shelve-backup/default.hg: file
  $ touch -t 200001010000 .hg/shelve-backup/default.hg
  $ f -t .hg/shelve-backup/default-1.hg
  .hg/shelve-backup/default-1.hg: file
  $ touch -t 200001010000 .hg/shelve-backup/default-1.hg

  $ hg unshelve
  unshelving change 'default-01'
  $ hg status -C
  M a/a
  A b.rename/b
    b/b
  A c.copy
    c
  R b/b
  $ hg shelve -l

(both of default.hg and default-1.hg should be still kept, because it
is difficult to decide actual order of them from same timestamp)

  $ ls .hg/shelve-backup/
  default-01.hg
  default-01.patch
  default-1.hg
  default-1.patch
  default.hg
  default.patch

  $ hg unshelve
  abort: no shelved changes to apply!
  [255]
  $ hg unshelve foo