tests/test-merge-subrepos.t

profiling: add statprof support for Chrome trace viewer rendering

We synthesize function call begin/end events from snapshots, and
try (configurably) to eliminate "noisy" stack frames.

Example invocation:

hg --config profiling.output=$HOME/Desktop/clone.json \
   --config profiling.statformat=chrome \
   --profile clone https://www.mercurial-scm.org/repo/hg

  $ hg init

  $ echo a > a
  $ hg ci -qAm 'add a'

  $ hg init subrepo
  $ echo 'subrepo = http://example.net/libfoo' > .hgsub
  $ hg ci -qAm 'added subrepo'

  $ hg up -qC 0
  $ echo ax > a
  $ hg ci -m 'changed a'
  created new head

  $ hg up -qC 1
  $ cd subrepo
  $ echo b > b
  $ hg add b
  $ cd ..

Should fail, since there are added files to subrepo:

  $ hg merge
  abort: uncommitted changes in subrepository 'subrepo'
  [255]