wrap: Fix diff_files not finding the patch to apply

[nirbheek]

The path to the patch must be provided relative to the working directory used to run the command: patch or git.

The feature doesn't work when using meson subprojects update without this fix.

[xclaesse]

Don't we have a unit test for this feature?

[codecov]

Codecov Report

Merging #10602 (f46c9a3) into master (f6a54de) will decrease coverage by 18.00%.
The diff coverage is n/a.

❗ Current head f46c9a3 differs from pull request most recent head 3e65456. Consider uploading reports for the commit 3e65456 to get more accurate results

@@             Coverage Diff             @@
##           master   #10602       +/-   ##
===========================================
- Coverage   68.31%   50.31%   -18.01%     
===========================================
  Files         203      203               
  Lines       44000    44000               
  Branches     9773     9755       -18     
===========================================
- Hits        30060    22139     -7921     
- Misses      11619    19859     +8240     
+ Partials     2321     2002      -319     

Impacted Files	Coverage Δ
modules/qt5.py	0.00% <0.00%> (-100.00%)	⬇️
modules/modtest.py	0.00% <0.00%> (-100.00%)	⬇️
scripts/run_tool.py	0.00% <0.00%> (-100.00%)	⬇️
scripts/msgfmthelper.py	0.00% <0.00%> (-100.00%)	⬇️
modules/keyval.py	0.00% <0.00%> (-95.24%)	⬇️
scripts/clangtidy.py	0.00% <0.00%> (-93.34%)	⬇️
scripts/vcstagger.py	0.00% <0.00%> (-91.67%)	⬇️
modules/unstable_icestorm.py	0.00% <0.00%> (-91.67%)	⬇️
modules/sourceset.py	0.00% <0.00%> (-90.54%)	⬇️
scripts/depscan.py	0.00% <0.00%> (-83.92%)	⬇️
... and 117 more

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[nirbheek]

Don't we have a unit test for this feature?

It works in the test because wrap.filesdir is an absolute path, probably because interpreter.py passes it an absolute path to the source directory. If you use meson subprojects update, the source directory is relative, and things fail.

Fixing merge request description...

[eli-schwartz]

Can we fix the commit description too? :)

[nirbheek]

Done.