Update mercurial repositories without removing directory and cloning again

[bugzilla-to-github]

This issue was created automatically by a script.

Bug 1609874

Bug Reporter: @mathjazz CC: @flodolo

We update Mercurial repositories by removing the directory first and cloning again. That's slower and causes issues like bug 1608660.

We should look into more elegant ways of reverting any local changes and updating the repo.

We tried that in the past, but failed: https://github.com/mozilla/pontoon/commit/85fb26b874a34e9eb544dba1b3333398a3c117f1

[bugzilla-to-github]

Comment Author: @flodolo

I see the comment says that we ended up with multiple heads. Isn't that what hg strip "roots(draft())" is there for? Any clue what failed?

[bugzilla-to-github]

Comment Author: @Pike

We should probably prune these days instead of strip. And then it'd not be roots.

[mathjazz]

Lowering priority, since we're moving L20n projects off of Mercurial.