feat: git change detection works on any commit

cmd/terramate/cli/cli.go

@@ -627,22 +627,16 @@ func (c *cli) setupGit() {
 		return
 	}
 
-	remoteCheckFailed := false
-
 	if err := c.prj.checkDefaultRemote(); err != nil {
 		if c.prj.git.remoteConfigured {
 			fatal(err, "checking git default remote")
-		} else {
-			remoteCheckFailed = true
 		}
 	}
 
 	if c.parsedArgs.GitChangeBase != "" {
-		c.prj.baseRef = c.parsedArgs.GitChangeBase
-	} else if remoteCheckFailed {
-		c.prj.baseRef = c.prj.defaultLocalBaseRef()
+		c.prj.baseRev = c.parsedArgs.GitChangeBase
 	} else {
-		c.prj.baseRef = c.prj.defaultBaseRef()
+		c.prj.baseRev = c.prj.selectChangeBase()
 	}
 }
 
@@ -763,7 +757,7 @@ func (c *cli) triggerStackByFilter() {
 		fatal(errors.E("trigger command expects either a stack path or the --experimental-status flag"))
 	}
 
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 	status := parseStatusFilter(c.parsedArgs.Experimental.Trigger.ExperimentalStatus)
 	stacksReport, err := c.listStacks(mgr, false, status)
 	if err != nil {
@@ -1311,7 +1305,7 @@ func (c *cli) printStacks() {
 		log.Fatal().Msg("the --why flag must be used together with --changed")
 	}
 
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 
 	status := parseStatusFilter(c.parsedArgs.List.ExperimentalStatus)
 	report, err := c.listStacks(mgr, c.parsedArgs.Changed, status)
@@ -1351,7 +1345,7 @@ func parseStatusFilter(strStatus string) cloudstack.FilterStatus {
 }
 
 func (c *cli) printRunEnv() {
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 	report, err := c.listStacks(mgr, c.parsedArgs.Changed, cloudstack.NoFilter)
 	if err != nil {
 		fatal(err, "listing stacks")
@@ -1579,7 +1573,7 @@ func (c *cli) generateDebug() {
 }
 
 func (c *cli) printStacksGlobals() {
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 	report, err := c.listStacks(mgr, c.parsedArgs.Changed, cloudstack.NoFilter)
 	if err != nil {
 		fatal(err, "listing stacks globals: listing stacks")
@@ -1613,7 +1607,7 @@ func (c *cli) printMetadata() {
 		Str("action", "cli.printMetadata()").
 		Logger()
 
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 	report, err := c.listStacks(mgr, c.parsedArgs.Changed, cloudstack.NoFilter)
 	if err != nil {
 		fatal(err, "loading metadata: listing stacks")
@@ -1677,7 +1671,7 @@ func (c *cli) checkGenCode() bool {
 }
 
 func (c *cli) ensureStackID() {
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 	report, err := c.listStacks(mgr, false, cloudstack.NoFilter)
 	if err != nil {
 		fatal(err, "listing stacks")
@@ -1922,7 +1916,7 @@ func (c *cli) friendlyFmtDir(dir string) (string, bool) {
 }
 
 func (c *cli) computeSelectedStacks(ensureCleanRepo bool) (config.List[*config.SortableStack], error) {
-	mgr := stack.NewManager(c.cfg(), c.prj.baseRef)
+	mgr := stack.NewManager(c.cfg(), c.prj.baseRev)
 
 	report, err := c.listStacks(mgr, c.parsedArgs.Changed, cloudstack.NoFilter)
 	if err != nil {

cmd/terramate/cli/project.go

@@ -20,7 +20,7 @@ type project struct {
 	wd             string
 	isRepo         bool
 	root           config.Root
-	baseRef        string
+	baseRev        string
 	normalizedRepo string
 
 	git struct {
@@ -63,25 +63,6 @@ func (p *project) prettyRepo() string {
 	return p.normalizedRepo
 }
 
-func (p *project) localDefaultBranchCommit() string {
-	if p.git.localDefaultBranchCommit != "" {
-		return p.git.localDefaultBranchCommit
-	}
-	logger := log.With().
-		Str("action", "localDefaultBranchCommit()").
-		Logger()
-
-	gitcfg := p.gitcfg()
-	refName := gitcfg.DefaultRemote + "/" + gitcfg.DefaultBranch
-	val, err := p.git.wrapper.RevParse(refName)
-	if err != nil {
-		logger.Fatal().Err(err).Send()
-	}
-
-	p.git.localDefaultBranchCommit = val
-	return val
-}
-
 func (p *project) isGitFeaturesEnabled() bool {
 	return p.isRepo && p.hasCommit()
 }
@@ -137,50 +118,48 @@ func (p *project) remoteDefaultCommit() string {
 	return p.git.remoteDefaultBranchCommit
 }
 
-func (p *project) isDefaultBranch() bool {
-	git := p.gitcfg()
-	branch, err := p.git.wrapper.CurrentBranch()
-	if err != nil {
-		// WHY?
-		// The current branch name (the symbolic-ref of the HEAD) is not always
-		// available, in this case we naively check if HEAD == local origin/main.
-		// This case usually happens in the git setup of CIs.
-		return p.localDefaultBranchCommit() == p.headCommit()
+// selectChangeBase returns the revision used for change comparison based on the current Git state.
+func (p *project) selectChangeBase() string {
+	gitcfg := p.gitcfg()
+	gw := p.git.wrapper
+
+	defaultBranchRev, _ := gw.RevParse(gitcfg.DefaultBranch)
+	if defaultBranchRev == "" {
+		// There's no default branch available, so we can't look for a common parent with it.
+		return gitcfg.DefaultBranchBaseRef
 	}
 
-	return branch == git.DefaultBranch
-}
+	branch, _ := gw.CurrentBranch()
 
-// defaultBaseRef returns the baseRef for the current git environment.
-func (p *project) defaultBaseRef() string {
-	git := p.gitcfg()
-	if p.isDefaultBranch() &&
-		p.remoteDefaultCommit() == p.headCommit() {
-		_, err := p.git.wrapper.RevParse(git.DefaultBranchBaseRef)
-		if err == nil {
-			return git.DefaultBranchBaseRef
+	// Either we are on a branch or at a detached HEAD.
+	if branch != "" {
+		if branch == gitcfg.DefaultBranch {
+			// We are at the tip of the default branch -> latest default commit.
+			return gitcfg.DefaultBranchBaseRef
+		}
+	} else {
+		headRev, _ := gw.RevParse("HEAD")
+		isDetachedDefaultBranchTip := headRev == defaultBranchRev
+		if isDetachedDefaultBranchTip {
+			// We are at the latest commit of the default branch.
+			return gitcfg.DefaultBranchBaseRef
 		}
-	}
-
-	return p.defaultBranchRef()
-}
 
-// defaultLocalBaseRef returns the baseRef in case there's no remote setup.
-func (p *project) defaultLocalBaseRef() string {
-	git := p.gitcfg()
-	if p.isDefaultBranch() {
-		_, err := p.git.wrapper.RevParse(git.DefaultBranchBaseRef)
-		if err == nil {
-			return git.DefaultBranchBaseRef
+		isDefaultBranchAncestor, _ := gw.IsFirstParentAncestor("HEAD", defaultBranchRev)
+		if isDefaultBranchAncestor {
+			// We are at an older commit of the default branch.
+			return gitcfg.DefaultBranchBaseRef
 		}
 	}
 
-	return git.DefaultBranch
-}
+	commonParentWithDefaultBranch, _ := gw.FindNearestCommonParent(defaultBranchRev, "HEAD")
+	if commonParentWithDefaultBranch != "" {
+		// We have a nearest common parent with the default branch. Similar to the historic merge base.
+		return commonParentWithDefaultBranch
+	}
 
-func (p project) defaultBranchRef() string {
-	git := p.gitcfg()
-	return git.DefaultRemote + "/" + git.DefaultBranch
+	// Fall back to default. Should never happen unless running on an isolated commit.
+	return gitcfg.DefaultBranchBaseRef
 }
 
 func (p *project) setDefaults() error {