How to use Visual Studio Code as the default MergeTool for mercurial

To change the default merge method, what is configuration is needed to provide the .hgrc file. I tried the google but it didn't work.

Solution

I assume you wanted to use "Visual Studio Code"'s version control - Merge Conflicts feature. And I guess that you wanted the same feature, but with mercurial's source control.

So, the first thing we have to do is to configure mercurial to use VSCode as the merge tool. To do it, I look at the following documentation.

Seems like the mercurial want to know the Registry value of VSCode for activating it. I looked around the internet and found this gitlab Issue with the relevant keys.

So the current additional configuration is:

[merge-tools]
vscode.regkey=SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{EA457B21-F73E-494C-ACAB-524FDE069978}_is1
vscode.regname=DisplayIcon
vscode.args= --wait $output
vscode.binary=False
vscode.gui=True
vscode.checkconflicts=True
vscode.premerge=keep

[extensions]
extdiff=

[merge-patterns]
*.*=vscode

[ui]
merge= :vscode

BAM! Works!

Possible problems

Missing line terminator

During the testing of this configuration, I encountered a problem when there is a conflict that has no line terminator (\n) at the end.

Notice: There is no a '\n' at the end of the file

file.txt (branch 'foo')

foo

file.txt (branch 'bar')

bar

The result of $output is:

file.txt (merge output)

<<<<<<< working copy
foo=======
bar>>>>>>> merge rev

and VSCode's merge conflict solver cannot detect this part of the code as a conflict because the code that detects ======= and >>>>>>> assumes that they are places at the begging of the line like this:

<<<<<<< working copy
foo
=======
bar
>>>>>>> merge rev

We can see this assumption here and here. I think it is perfectly fine, but I had to add this to avoid any future problems.

Here you have it, have fun.