Use `git update-ref --stdin -z` to speed up TestEnv.set_repo_refs

What does this MR do?

Switches from executing git update-ref ~30 times per create(:project) call to executing it once only.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

The test suite is slow. This is part of why.

Screenshots (if relevant)

public_access_spec.rb.dump.before public_access_spec.rb.dump.after

gitlab-mbp:gitlab lupine$ stackprof --select-names TestEnv public_access_spec.rb.dump.before
==================================
  Mode: wall(1000)
  Samples: 374178 (6.99% miss rate)
  GC: 55991 (14.96%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
     42353  (11.3%)       13937   (3.7%)     TestEnv#set_repo_refs
        61   (0.0%)           5   (0.0%)     TestEnv#setup_repo
         1   (0.0%)           1   (0.0%)     TestEnv#warm_asset_cache?
         1   (0.0%)           1   (0.0%)     TestEnv#factory_repo_path_bare
      4414   (1.2%)           0   (0.0%)     TestEnv#warm_asset_cache
      3274   (0.9%)           0   (0.0%)     TestEnv#clean_test_path
      1698   (0.5%)           0   (0.0%)     TestEnv#init
        49   (0.0%)           0   (0.0%)     TestEnv#setup_factory_repo
        12   (0.0%)           0   (0.0%)     TestEnv#setup_forked_repo
     15315   (4.1%)           0   (0.0%)     TestEnv#copy_repo
gitlab-mbp:gitlab lupine$ stackprof --select-names TestEnv public_access_spec.rb.dump.after
==================================
  Mode: wall(1000)
  Samples: 385945 (3.33% miss rate)
  GC: 56259 (14.58%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
      2069   (0.5%)         517   (0.1%)     TestEnv#set_repo_refs
         5   (0.0%)           3   (0.0%)     TestEnv#setup_repo
         3   (0.0%)           3   (0.0%)     TestEnv#factory_repo_path
         5   (0.0%)           2   (0.0%)     TestEnv#factory_repo_path_bare
      6431   (1.7%)           0   (0.0%)     TestEnv#warm_asset_cache
        12   (0.0%)           0   (0.0%)     TestEnv#clean_test_path
        12   (0.0%)           0   (0.0%)     TestEnv#init
         3   (0.0%)           0   (0.0%)     TestEnv#setup_factory_repo
         1   (0.0%)           0   (0.0%)     TestEnv#forked_repo_path
         3   (0.0%)           0   (0.0%)     TestEnv#setup_forked_repo
      1991   (0.5%)           0   (0.0%)     TestEnv#copy_repo
gitlab-mbp:gitlab lupine$

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Related to #23034 (closed)

Reassigned to @nick.thomas

Marked this merge request as a Work In Progress

Added 26 commits:

• ab89de0e...5ef2bd19 - 25 commits from branch gitlab-org:master
• c71d1134 - Use git update-ref --stdin -z to speed up TestEnv.set_repo_refs

Compare with previous version

Added 1 commit:

• 8642fc7d - Use git update-ref --stdin -z to speed up TestEnv.set_repo_refs

Compare with previous version

Unmarked this merge request as a Work In Progress

Reassigned to @yorickpeterse

Marked the task All builds are passing as completed

Marked the task Added for this feature/bug as completed

Marked the task API support added as completed

Marked the task Documentation created/updated as completed

Marked the task Conform by the merge request performance guides as completed

Marked the task Conform by the style guides as completed

Marked the task Squashed related commits together as completed

Marked the task Branch has no merge conflicts with master (if it does - rebase it please) as completed

@yorickpeterse what do you think? I've got a separate (WIP) MR to switch create(:project) to create(:empty_project) where possible, but it's not possible anywhere an MR is being referenced in a test, so this is still helpful.

Reassigned to @nick.thomas

@nick.thomas One pedantic little comment, other than that this looks good to me

Added 1 commit:

• 29668aec - Use git update-ref --stdin -z to speed up TestEnv.set_repo_refs

Compare with previous version

Resolved all discussions