Use three-way diffs for merge conflicts

[robmoss]

As part of the initial setup instructions, we now set the merge-conflict style to 'diff3', which also shows the original lines. This extra information can help to decide how to best resolve a conflict.

In the first example conflict, it changes the diff from:

diff --cc test.txt
index 18712c4,bc576a6..0000000
--- a/test.txt
+++ b/test.txt
@@@ -1,3 -1,3 +1,7 @@@
  First line
++<<<<<<< ours
 +A different second line
++=======
+ My new second line
++>>>>>>> theirs
  Third line

to:

diff --cc test.txt
index 18712c4,bc576a6..0000000
--- a/test.txt
+++ b/test.txt
@@@ -1,3 -1,3 +1,7 @@@
  First line
++<<<<<<< ours
 +A different second line
++||||||| base
++Second line
++=======
+ My new second line
++>>>>>>> theirs
  Third line

[github-actions]

PR Preview Action v1.4.4
Preview removed because the pull request was closed.
2023-12-05 23:57 UTC

[EamonConway]

I have provided an additional info section for the --global flag.
I think it is important that people know they can change the configuration on a repo by repo basis.
I can confirm that this hosts locally successfully.
Happy for this to be merged if you agree.

[robmoss]

Very nice, thank you!