tests/test-merge4.t

subrepos: abort commit by default if a subrepo is dirty (BC)

This changeset flips the default value of ui.commitsubrepos setting
from True to False and adds a --subrepos flag to commit.

The commit, status, and diff commands behave like this with regard to
recusion and the ui.commitsubrepos setting:

          | recurses      | recurses
          | by default    | with --subrepos
  --------+---------------+----------------
  commit: | commitsubrepo | True
  status: | False         | True
  diff:   | False         | True

By changing the default from True to False, the table becomes
consistent in the two columns:

* without --subrepos on the command line, commit will abort if a
  subrepo is dirty and status/diff wont show changes inside subrepos.

* with --subrepos, all three commands will recurse.

A --subrepos flag on the command line overrides the config settin.g

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg update 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #2"
  created new head
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ rm b
  $ echo This is file c22 > c
  $ hg commit -m "commit #3"