Changes to githead.go. All files

githead.go

new file mode 100644@@ -0,0 +1,147 @@+package main++import (+	"bufio"+	"context"+	"os"+	"path/filepath"+	"strings"+)++// repo is the git repo a directory lies in, as git found it, or git's+// complaint when it lies in none.+type repo struct {+	gitDir, common, top string+	complaint           string+}++// repoAt asks git once which repo dir lies in, so git's own checks, such as+// safe.directory, decide. The answer is kept until a .git appears or goes+// where it would change: between dir and the repo's top, or above dir when+// dir lies in no repo.+func repoAt(ctx context.Context, dir string) repo {+	key := "repo\x00" + dir+	if v, ok := gitCache.get(key); ok {+		if r := v.(repo); r.holds(dir) {+			return r+		}+		gitCache.drop(key)+	}+	var r repo+	out, err := git(ctx, dir, "rev-parse", "--path-format=absolute", "--git-dir", "--git-common-dir", "--show-toplevel")+	if err != nil {+		// Inside a git directory there is no work tree to name.+		out, err = git(ctx, dir, "rev-parse", "--path-format=absolute", "--git-dir", "--git-common-dir")+	}+	if err != nil {+		r.complaint = string(out) + err.Error()+	} else {+		f := strings.Split(strings.TrimSpace(string(out)), "\n")+		r.gitDir, r.common = f[0], f[1]+		if len(f) > 2 {+			r.top = f[2]+		}+	}+	gitCache.put(key, r, int64(len(r.gitDir)+len(r.common)+len(r.top)+len(r.complaint)))+	return r+}++// holds reports whether r still answers for dir: its git directory is+// there, and no .git has appeared or gone in the levels that decide.+func (r repo) holds(dir string) bool {+	if r.complaint != "" {+		for d := dir; ; d = filepath.Dir(d) {+			if exists(filepath.Join(d, ".git")) {+				return false+			}+			if d == filepath.Dir(d) {+				return true+			}+		}+	}+	if !exists(filepath.Join(r.gitDir, "HEAD")) {+		return false+	}+	if r.top == "" {+		return true+	}+	for d := dir; d != r.top; d = filepath.Dir(d) {+		if exists(filepath.Join(d, ".git")) || d == filepath.Dir(d) {+			return false+		}+	}+	return exists(filepath.Join(r.top, ".git"))+}++func exists(p string) bool {+	_, err := os.Lstat(p)+	return err == nil+}++// head names the commit HEAD points at. It reads the repo's files, which+// takes microseconds where git takes a millisecond, and asks git only for+// what it cannot read: a reftable store or a ref it does not find.+func (r repo) head(ctx context.Context) string {+	if h, ok := r.readHead(); ok {+		return h+	}+	out, err := git(ctx, r.gitDir, "rev-parse", "HEAD")+	if err != nil {+		return "no HEAD: " + err.Error()+	}+	return strings.TrimSpace(string(out))+}++func (r repo) readHead() (string, bool) {+	if exists(filepath.Join(r.common, "reftable")) {+		return "", false+	}+	ref := "HEAD"+	for range 5 {+		val, ok := r.readRef(ref)+		if !ok {+			return "", false+		}+		target, symbolic := strings.CutPrefix(val, "ref: ")+		if !symbolic {+			return val, isHash(val)+		}+		ref = target+	}+	return "", false+}++// readRef reads a ref from the worktree's git directory, then the common+// one, then packed-refs.+func (r repo) readRef(ref string) (string, bool) {+	for _, d := range []string{r.gitDir, r.common} {+		if b, err := os.ReadFile(filepath.Join(d, filepath.FromSlash(ref))); err == nil {+			return strings.TrimSpace(string(b)), true+		}+	}+	f, err := os.Open(filepath.Join(r.common, "packed-refs"))+	if err != nil {+		return "", false+	}+	defer f.Close()+	sc := bufio.NewScanner(f)+	for sc.Scan() {+		hash, name, ok := strings.Cut(sc.Text(), " ")+		if ok && name == ref {+			return hash, true+		}+	}+	return "", false+}++func isHash(s string) bool {+	if len(s) != 40 && len(s) != 64 {+		return false+	}+	for _, c := range s {+		if !(c >= '0' && c <= '9' || c >= 'a' && c <= 'f') {+			return false+		}+	}+	return true+}