Improve TestPatch to make it much quicker when there are no conflicts and large files

[zeripath]

Prior to this PR essentially the test patch code was git diff -p --binary mergebase base head | git apply --check --cached

This is extremely slow if there are large binary files and the implementation dumped large temporary files on to the system.

We therefore propose a different option here:

• git read-tree -m to attempt the basic merge
• git status --porcelain can then be used to find the conflicts here.
• we can then limit the diff patch to only the conflicts - and we will drop the binary diff as the whitespace diffs matching is unlikely to be of help.

Signed-off-by: Andrew Thornton art27@cantab.net

[zeripath]

This PR should save at least 12s in our tests.

Was:
+++ TestGit/HTTP/MergeFork/CreatePRAndMerge is a slow test (took 40.292540645s)

Is:
+++ TestGit/SSH/MergeFork/CreatePRAndMerge is a slow test (took 34.214094827s)

[zeripath]

Ready

[zeripath]

@a1012112796 All of your changes are covered in

git read-tree base
git read-tree -m --aggressive merge-base base tracking
git status --porcelain

and are much faster and better covered in that.

git read-tree -m --aggressive handles renames correctly amongst other things - your changes do not.

[a1012112796]

Some logic simplify about else :)

[a1012112796]

Now this function is a little long(near 190 lines) ..........
Maybe it's better to split it...

[zeripath]

Have split it up and added a few more comments

[codecov-commenter]

Codecov Report

Merging #15314 (a2dbf1f) into main (17be645) will increase coverage by 0.00%.
The diff coverage is 68.42%.

@@           Coverage Diff           @@
##             main   #15314   +/-   ##
=======================================
  Coverage   44.01%   44.01%           
=======================================
  Files         681      681           
  Lines       82351    82393   +42     
=======================================
+ Hits        36249    36269   +20     
- Misses      40194    40213   +19     
- Partials     5908     5911    +3     

Impacted Files	Coverage Δ
services/pull/patch.go	53.88% <68.42%> (-0.36%)	⬇️
models/unit.go	46.57% <0.00%> (-2.74%)	⬇️
modules/log/event.go	59.90% <0.00%> (-1.89%)	⬇️
routers/repo/view.go	40.66% <0.00%> (-0.59%)	⬇️
modules/queue/workerpool.go	53.81% <0.00%> (+0.76%)	⬆️
modules/process/manager.go	75.30% <0.00%> (+2.46%)	⬆️
modules/queue/queue_channel.go	96.66% <0.00%> (+5.00%)	⬆️

---

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[6543]

this did not recognize a custom created conflict:

to reproduce:

• create two branches from master (A & B)
• add file CONFL with content aaa\n to branch A
• add file CONFL with content bbb\n to branch B
• create pull from A to master
• create pull from B to master
• merge B
• look at A: still show "merge ..." button!

[zeripath]

Damn - I'll take a look. In the meantime let me mark this as WIP

[zeripath]

Replaced by #18004