migrations: add test for importing pull requests in gitea uploader

[singuliere]

See original merge request from Loïc Dachary @ forgefriends

---

The gitea_uploader.go is modified in a minimal way to move around 100 lines to the updateGitForPullRequest, the code logic is otherwise not modified. Tests are written to provide 100% coverage, except for the system errors from os.Create etc.

[codecov-commenter]

Codecov Report

Merging #18752 (22756fe) into main (4d93984) will decrease coverage by 0.00%.
The diff coverage is 45.56%.

@@            Coverage Diff             @@
##             main   #18752      +/-   ##
==========================================
- Coverage   46.64%   46.63%   -0.01%     
==========================================
  Files         846      854       +8     
  Lines      121331   122516    +1185     
==========================================
+ Hits        56595    57136     +541     
- Misses      57859    58490     +631     
- Partials     6877     6890      +13     

Impacted Files	Coverage Δ
cmd/admin_auth_ldap.go	79.59% <ø> (ø)
models/auth/webauthn.go	43.11% <ø> (ø)
models/org.go	73.88% <0.00%> (+0.21%)	⬆️
modules/git/pipeline/lfs_nogogit.go	0.00% <0.00%> (ø)
modules/git/pipeline/namerev.go	0.00% <0.00%> (ø)
modules/graceful/manager.go	22.16% <0.00%> (-0.13%)	⬇️
modules/graceful/manager_unix.go	38.88% <0.00%> (-0.95%)	⬇️
modules/log/conn.go	79.71% <0.00%> (-2.38%)	⬇️
modules/log/console.go	63.41% <0.00%> (-3.26%)	⬇️
modules/log/file.go	70.58% <0.00%> (-0.94%)	⬇️
... and 95 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d5a4c55...22756fe. Read the comment docs.

[singuliere]

make l-g-t-m work

[singuliere]

make l-g-t-m work