fix(git): default to the gc maintenance strategy (#40022)

Git 2.54 made "geometric" the default auto-maintenance strategy. Pushes
wait for its foreground reflog expiry
(https://github.com/go-gitea/gitea/issues/39693), and its detached
repacks race with filesystem operations, as in
https://github.com/go-gitea/gitea/actions/runs/40236681252/job/121299686933.
Pin the pre-2.54 "gc" strategy, older git ignores it.

https://github.com/go-gitea/gitea/pull/39745 is the more complete fix
which disables the auto-maintenance.

custom/conf/app.example.ini

@@ -810,6 +810,7 @@ LEVEL = Info
 ;[git.config]
 ;diff.algorithm = histogram
 ;core.logAllRefUpdates = true
+;maintenance.strategy = gc
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

modules/setting/git.go

@@ -87,6 +87,7 @@ func loadGitFrom(rootCfg ConfigProvider) {
 	GitConfig.Options = make(map[string]string)
 	GitConfig.SetOption("diff.algorithm", "histogram")
 	GitConfig.SetOption("core.logAllRefUpdates", "true")
+	GitConfig.SetOption("maintenance.strategy", "gc") // git 2.54's push-time default "geometric" delays pushes and repacks concurrently with other writes
 
 	for _, key := range secGitConfig.Keys() {
 		GitConfig.SetOption(key.Name(), key.String())

modules/setting/git_test.go

@@ -27,6 +27,7 @@ a.b = 1
 	loadGitFrom(cfg)
 	assert.Equal(t, "1", GitConfig.Options["a.b"])
 	assert.Equal(t, "histogram", GitConfig.Options["diff.algorithm"])
+	assert.Equal(t, "gc", GitConfig.Options["maintenance.strategy"])
 
 	cfg, err = NewConfigProviderFromData(`
 [git.config]