Update to Mercurial 6.5.1

I'll be updating the included Mercurial to 6.5.1, so that we can get rid of Python 2 and deploy Python 3 alongside Chorus. Some of my findings are:

Dropping in the 6.5.1 zip file, a lot of tests fail because fixutf8 is written for Python 2 only
If I disable fixutf8 entirely, nearly all the tests pass, so it seems to no longer be needed with Mercurial 6.5.1
The four failing tests include two checking for the fixutf8 extension (no problem), and two real failures
The real failure "local changed file that remote deleted" and "remote changed file that local deleted"
Those are caused by a change in Mercurial 3.7, where the default resolution for changed/deleted conflicts (which used to be to keep the changed file) was changed to "leave unresolved"
There's Chorus code that looks for a prompt from Mercurial containing the words "(c)hanged" and "(d)eleted" and sends a "c" to say "Hey, keep the changed file", but it is no longer working, at least by default
It appears that the Mercurial code ignores stdin for prompts unless it's from a real terminal, i.e. if stdin is redirected from a pipe then Mercurial just goes with the default for prompts
You can get around this by setting "ui.interactive = True" in the mercurial.ini file, or by making the following change to the installed Mercurial:

diff -ur mercurial-6.5.1/mercurial/filemerge.py Mercurial/mercurial/filemerge.py
--- mercurial-6.5.1/mercurial/filemerge.py  2023-08-07 16:05:26.000000000 +0700
+++ Mercurial/mercurial/filemerge.py    2023-11-29 12:35:02.753765548 +0700
@@ -322,10 +322,10 @@
     prompts[b'fd'] = uipathfn(fd)
     try:
         if other.fctx.isabsent():
-            index = ui.promptchoice(_localchangedotherdeletedmsg % prompts, 2)
+            index = ui.promptchoice(_localchangedotherdeletedmsg % prompts, 0)
             choice = [b'local', b'other', b'unresolved'][index]
         elif local.fctx.isabsent():
-            index = ui.promptchoice(_otherchangedlocaldeletedmsg % prompts, 2)
+            index = ui.promptchoice(_otherchangedlocaldeletedmsg % prompts, 0)
             choice = [b'other', b'local', b'unresolved'][index]
         else:
             # IMPORTANT: keep the last line of this prompt ("What do you want to

That changes the default for those two prompts from "(u)nresolved" to "(c)hanged", which is what we want
That's a little brittle as we'll have to make the same change again in the future any time we update the included Mercurial version, however it's not a difficult change to make so I think it will be worth it if "ui.interactive = True" fails to work for us for some reason

Further findings: we do still need to use fixutf8.py on Windows. The tests were passing earlier because the default test project name ("test projéct") was something that could be encoded in cp-1252 (the Windows "equivalent" of latin-1 with extra characters). Changing the test project name to something with non-Latin characters resulted in a bunch of test failures, mostly caused by some internal Mercurial functions not quite expecting the results that they got back from certain Python 3 library calls. (For example, if you do os.path.realpath(''), you get the current working directory. But for some reason, if and only if the current working directory contains non-Latin characters, you get the current working directory with \. appended. This causes the Mercurial code that says "is this file in the current repo?" to fail, because it relies on a string comparison between the filename and the current working directory.)

But I've gotten a version of fixutf8.py running correctly under Python 3 and Mercurial 6.5.1. I'll submit a PR to update both Mercurial and MercurialExtensions accordingly; once that PR is merged into Mercurial4Chorus, we can submit a PR for Chorus that pulls the new Mecurial4Chorus package and makes the right changes in Chorus as well (like no longer messing with encodings in Program.cs).

Long story short, PR incoming to update to Mercurial 6.5.1.

sillsdev / Mercurial4Chorus

Update to Mercurial 6.5.1 #10