tests/test-issue619.t

color: support a different color mode when the pager is active

MSYS on Windows has a terminal that supports the "win32" color mode
(which "auto" properly detects for us). However, a popularily configured
pager in that environment (GNU less) only supports the "ansi" color
mode.

This patch teaches color about a new config option: pagermode. It
behaves like "mode" but is only consulted when the pager is active for
the current command. MSYS users can now set "pagermode = ansi" and get a
colorful experience that just works. Previously, MSYS users would have
to live without color when using GNU less as the pager, would have to
manually configure the pager to attend every command, or would have
gibberish if "ansi" was used without the pager.

http://mercurial.selenic.com/bts/issue619

  $ hg init
  $ echo a > a
  $ hg ci -Ama
  adding a

  $ echo b > b
  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -Amb
  adding b

  $ hg co -C 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

Fast-forward:

  $ hg merge b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -Ammerge

Bogus fast-forward should fail:

  $ hg merge b
  abort: merging with a working directory ancestor has no effect
  [255]

Even with strange revset (issue4465)

  $ hg merge ::.
  abort: merging with a working directory ancestor has no effect
  [255]