Fix Open with Diff Tool does not work with staged renamed file in FormCommit dialog

[hieuxlu]

Fixes #8600

Proposed changes

• Use UICommands.OpenWithDiffTool, just like RevisionDiffControl, with diffKind = RevisionDiffKind.DiffAB

Screenshots

Before

After

Test methodology

• Manual test. FormCommit has no unit test. I found an integration test for FormCommit, but there's no test for difftool yet.

Test environment(s)

• Git 2.28.0.windows.1
• Microsoft Windows NT 10.0.17763.0
• .NET Framework 4.8.4250.0
• DPI 144dpi (150% scaling)

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✒️ I contribute this code under The Developer Certificate of Origin.

[codecov]

Codecov Report

Merging #8601 (a087f9b) into master (45ffd65) will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #8601      +/-   ##
==========================================
- Coverage   55.13%   55.10%   -0.03%     
==========================================
  Files         904      904              
  Lines       65466    65465       -1     
  Branches    11853    11852       -1     
==========================================
- Hits        36094    36077      -17     
- Misses      26548    26560      +12     
- Partials     2824     2828       +4     

Flag	Coverage Δ
production	42.12% <0.00%> (-0.03%)	⬇️
tests	94.84% <ø> (-0.02%)	⬇️

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[gerhardol]

Manual test. FormCommit has no unit test. I found an integration test for FormCommit, but there's no test for difftool yet.

This is supposed to be tested with the revisionDiffProvider, but the UI code must call the correct methods too...

Checked other use of Module.OpenWithDifftool() too, no issues seen.
(RevTree has no direct access to renamed files, always compares to worktree.)

[mstv]

Thank you

[mstv]

@msftbot merge in 1 day

[ghost]

Hello @mstv!

Because you've given me some instructions on how to help merge this pull request, I'll be modifying my merge approach. Here's how I understand your requirements for merging this pull request:

• I won't merge this pull request until after the UTC date Mon, 09 Nov 2020 21:25:04 GMT, which is in 1 day

If this doesn't seem right to you, you can tell me to cancel these instructions and use the auto-merge policy that has been configured for this repository. Try telling me "forget everything I just told you".