tests/test-close-head.t

mergestate: determine if active without looking for state files on disk

I couldn't think of a reason that we need to check state files on disk
to determine if a merge is active. I could imagine them being for
there for detecting broken state files that would then be cleaned up
by some later command, but we always delete the entire `.hg/merge/`
tree, so that doesn't seem to be it.

The checks were added in 4e932dc5c113 (resolve: abort when not
applicable (BC), 2014-04-18). Perhaps there were needed for that and
then made obsolete by 6062593d8b06 (resolve: don't abort resolve -l
even when no merge is in progress, 2014-05-23).

The reason I want to delete the checks is that I think `ms =
mergestate.read(repo); ms.active() and ms.local` should be a valid
pattern, but it crashes when the merge state file is an empty file if
we consider mere presence of the file as "active".

Differential Revision: https://phab.mercurial-scm.org/D8118

  $ hg init test-content
  $ cd test-content
  $ hg debugbuilddag '+2*2*3*4+7'
  $ hg bookmark -r 1 @
  $ hg log -G --template '{rev}:{node|short}'
  o  11:1d876b1f862c
  |
  o  10:ea5f71948eb8
  |
  o  9:f1b0356d867a
  |
  o  8:e8d1253fb0d7
  |
  o  7:d423bbba4459
  |
  o  6:a2f58e9c1e56
  |
  o  5:3a367db1fabc
  |
  o  4:e7bd5218ca15
  |
  | o  3:6100d3090acf
  |/
  | o  2:fa942426a6fd
  |/
  | o  1:66f7d451a68b
  |/
  o  0:1ea73414a91b
  
  $ hg --config extensions.closehead= close-head -m 'Not a head' 0 1
  abort: revision is not an open head: 0
  [255]
  $ hg --config extensions.closehead= close-head -m 'Not a head' -r 0 1
  abort: revision is not an open head: 0
  [255]
  $ hg id
  000000000000
  $ hg --config extensions.closehead= close-head -m 'Close old heads' -r 1 2
  $ hg id
  000000000000
  $ hg bookmark
     @                         1:66f7d451a68b
  $ hg heads
  changeset:   11:1d876b1f862c
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:11 1970 +0000
  summary:     r11
  
  changeset:   3:6100d3090acf
  parent:      0:1ea73414a91b
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     r3
  
  $ hg --config extensions.closehead= close-head -m 'Close more old heads' -r 11
  $ hg heads
  changeset:   3:6100d3090acf
  parent:      0:1ea73414a91b
  user:        debugbuilddag
  date:        Thu Jan 01 00:00:03 1970 +0000
  summary:     r3
  
  $ hg --config extensions.closehead= close-head -m 'Not a head' 0
  abort: revision is not an open head: 0
  [255]
  $ hg --config extensions.closehead= close-head -m 'Already closed head' 1
  abort: revision is not an open head: 1
  [255]

  $ hg init ../test-empty
  $ cd ../test-empty
  $ hg debugbuilddag '+1'
  $ hg log -G --template '{rev}:{node|short}'
  o  0:1ea73414a91b
  
  $ hg --config extensions.closehead= close-head -m 'Close initial revision' 0
  $ hg heads
  [1]