Re: automerge implementation ideas for Windows

On Thu, Jan 21, 2021 at 02:50:12PM -0800, Junio C Hamano wrote:

Agreed. What are your thoughts on the #2 approach?

I noticed the comment in `git/xdiff-interface.h` about xdiff's gigabyte limit so I created a 973 MB text file with a conflict and ran #2 through a few mergetools to see how it went. I put /usr/bin/time in front of the two `git merge-file` invocations. I know one person's machine is not a benchmark but perhaps it's a discussion point?

Each `git merge-file` call took ~11 seconds on my middle-tier laptop and did not use enough RAM to hit swap.

Writing the near-gigabyte LOCAL, BASE, REMOTE, & BACKUP files went pretty quick. The mergetools themselves had mixed results:

- vimdiff took several minutes (and a lot of swap) to open all four
  files but did eventually work.
- tkdiff crashed.
- Meld spun for ~10 minutes and never opened.

My takeaway: when trying to use a mergetool on a very large file, the two `git merge-file` invocations are not likely to be where the performance concern is. #2 is my preferred approach so far.