feat(gitea): pull-request create/list/get/merge endpoints

internal/fakegitea/fakegitea.go

@@ -9,6 +9,8 @@
 package fakegitea
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -206,8 +208,10 @@ func (s *Server) addRepoLocked(owner, name, defaultBranch string, branches []str
 }
 
 func (st *repoState) addBranch(name string) string {
-	// Deterministic distinct 40-hex shas (fake but well-formed).
-	sha := fmt.Sprintf("%040x", len(st.order)+1)
+	// Distinct, well-formed 40-hex shas derived from the branch key, so
+	// short-sha (>= 7 chars) resolution is unambiguous like real git.
+	sum := sha256.Sum256([]byte(st.repo.FullName + "/" + name))
+	sha := hex.EncodeToString(sum[:])[:40]
 	if _, ok := st.branches[name]; !ok {
 		st.order = append(st.order, name)
 	}
@@ -464,14 +468,17 @@ func (s *Server) listBranches(owner, name string) (int, string) {
 }
 
 // resolveRef maps a ref (full sha, sha prefix, or branch name) to a commit
-// sha; ok=false when nothing matches.
+// sha; ok=false when nothing matches. Prefix matches scan branches in
+// insertion order for determinism.
 func (st *repoState) resolveRef(ref string) (string, bool) {
 	if sha, ok := st.branches[ref]; ok {
 		return sha, true
 	}
-	for _, sha := range st.branches {
-		if strings.HasPrefix(sha, ref) && len(ref) >= 7 {
-			return sha, true
+	if len(ref) >= 7 {
+		for _, b := range st.order {
+			if strings.HasPrefix(st.branches[b], ref) {
+				return st.branches[b], true
+			}
 		}
 	}
 	return "", false