fix(git): leave reflog expiry to git's defaults (#39703) (#39711)

Backport #39703 by @silverwind

Gitea's default `gc.reflogExpire = 90` is parsed by git as
`1990-<month>-<day>`, currently `1990-10-09`, so reachable reflog
entries never expired.

Since git 2.54, auto maintenance runs its reflog-expire task in the
foreground of every push, and its trigger ignores reachability, so busy
repos rerun `git reflog expire --all` on every push without pruning
anything, stalling large repos for over a minute.

- Stop setting `gc.reflogExpire` so git's own defaults apply, and remove
the `90` written by earlier versions
- Treat the legacy `[git.reflog] EXPIRATION` as days, as documented

The next push to each repo prunes the accumulated entries once.

Fixes: https://github.com/go-gitea/gitea/issues/39693

Co-authored-by: silverwind <me@silverwind.io>

custom/conf/app.example.ini

@@ -810,7 +810,6 @@ LEVEL = Info
 ;[git.config]
 ;diff.algorithm = histogram
 ;core.logAllRefUpdates = true
-;gc.reflogExpire = 90
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

modules/git/config.go

@@ -125,6 +125,11 @@ func syncGitConfig(ctx context.Context) (err error) {
 		return err
 	}
 
+	// Gitea used to write "90", which git reads as a date in 1990
+	if err := configUnsetAll(ctx, "gc.reflogExpire", "90"); err != nil {
+		return err
+	}
+
 	// Apply user's git config options last so they take precedence over builtin defaults
 	for k, v := range setting.GitConfig.Options {
 		if err = configSet(ctx, strings.ToLower(k), v); err != nil {

modules/git/config_test.go

@@ -60,8 +60,10 @@ func TestSyncGitConfig(t *testing.T) {
 	defer test.MockVariableValue(&setting.GitConfig)()
 
 	assert.Empty(t, setting.GitConfig.Options)
+	assert.NoError(t, configSet(t.Context(), "gc.reflogExpire", "90"))
 	assert.NoError(t, syncGitConfig(t.Context()))
 	assert.True(t, gitConfigContains("commitGraph = true")) // builtin default config
+	assert.False(t, gitConfigContains("reflogExpire"))
 
 	setting.GitConfig.Options["sync-test.cfg-key-a"] = "CfgValA"
 	setting.GitConfig.Options["core.commitgraph"] = "false"

modules/setting/git.go

@@ -89,7 +89,6 @@ func loadGitFrom(rootCfg ConfigProvider) {
 	GitConfig.Options = make(map[string]string)
 	GitConfig.SetOption("diff.algorithm", "histogram")
 	GitConfig.SetOption("core.logAllRefUpdates", "true")
-	GitConfig.SetOption("gc.reflogExpire", "90")
 
 	secGitReflog := rootCfg.Section("git.reflog")
 	if secGitReflog.HasKey("ENABLED") {
@@ -97,8 +96,8 @@ func loadGitFrom(rootCfg ConfigProvider) {
 		GitConfig.SetOption("core.logAllRefUpdates", secGitReflog.Key("ENABLED").In("true", []string{"true", "false"}))
 	}
 	if secGitReflog.HasKey("EXPIRATION") {
-		deprecatedSetting(rootCfg, "git.reflog", "EXPIRATION", "git.config", "core.reflogExpire", "1.21")
-		GitConfig.SetOption("gc.reflogExpire", secGitReflog.Key("EXPIRATION").String())
+		deprecatedSetting(rootCfg, "git.reflog", "EXPIRATION", "git.config", "gc.reflogExpire", "1.21")
+		GitConfig.SetOption("gc.reflogExpire", secGitReflog.Key("EXPIRATION").String()+".days")
 	}
 
 	for _, key := range secGitConfig.Keys() {

modules/setting/git_test.go

@@ -38,8 +38,8 @@ diff.algorithm = other
 }
 
 func TestGitReflog(t *testing.T) {
-	defer test.MockVariableValue(&Git)
-	defer test.MockVariableValue(&GitConfig)
+	defer test.MockVariableValue(&Git)()
+	defer test.MockVariableValue(&GitConfig)()
 
 	// default reflog config without legacy options
 	cfg, err := NewConfigProviderFromData(``)
@@ -47,7 +47,7 @@ func TestGitReflog(t *testing.T) {
 	loadGitFrom(cfg)
 
 	assert.Equal(t, "true", GitConfig.GetOption("core.logAllRefUpdates"))
-	assert.Equal(t, "90", GitConfig.GetOption("gc.reflogExpire"))
+	assert.Empty(t, GitConfig.GetOption("gc.reflogExpire"))
 
 	// custom reflog config by legacy options
 	cfg, err = NewConfigProviderFromData(`
@@ -59,5 +59,5 @@ EXPIRATION = 123
 	loadGitFrom(cfg)
 
 	assert.Equal(t, "false", GitConfig.GetOption("core.logAllRefUpdates"))
-	assert.Equal(t, "123", GitConfig.GetOption("gc.reflogExpire"))
+	assert.Equal(t, "123.days", GitConfig.GetOption("gc.reflogExpire"))
 }