D385: drawdag: allow override file contents via comments

[quark (Jun Wu)]

quark added inline comments.

INLINE COMMENTS

> martinvonz wrote in test-drawdag.t:243
> Does it support creating graphs of resolved conflicts as follows?
> 
>   > C       # A/f = a
>   > |\      # B/f = b
>   > A B     # C/f = c

Yes. I uses `=` to indicate "replace the content". In the future we might want `+=` to do "append content" etc.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D385

To: quark, #hg-reviewers
Cc: martinvonz, mercurial-devel