Make API "compare" accept commit IDs (#32801)

modules/git/commit.go

@@ -474,3 +474,17 @@ func (c *Commit) GetRepositoryDefaultPublicGPGKey(forceUpdate bool) (*GPGSetting
 	}
 	return c.repo.GetDefaultPublicGPGKey(forceUpdate)
 }
+
+func IsStringLikelyCommitID(objFmt ObjectFormat, s string, minLength ...int) bool {
+	minLen := util.OptionalArg(minLength, objFmt.FullLength())
+	if len(s) < minLen || len(s) > objFmt.FullLength() {
+		return false
+	}
+	for _, c := range s {
+		isHex := (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')
+		if !isHex {
+			return false
+		}
+	}
+	return true
+}

modules/git/ref.go

@@ -142,7 +142,6 @@ func (ref RefName) RemoteName() string {
 
 // ShortName returns the short name of the reference name
 func (ref RefName) ShortName() string {
-	refName := string(ref)
 	if ref.IsBranch() {
 		return ref.BranchName()
 	}
@@ -158,8 +157,7 @@ func (ref RefName) ShortName() string {
 	if ref.IsFor() {
 		return ref.ForBranchName()
 	}
-
-	return refName
+	return string(ref) // usually it is a commit ID
 }
 
 // RefGroup returns the group type of the reference

modules/git/repo_ref.go

@@ -61,3 +61,31 @@ func parseTags(refs []string) []string {
 	}
 	return results
 }
+
+// UnstableGuessRefByShortName does the best guess to see whether a "short name" provided by user is a branch, tag or commit.
+// It could guess wrongly if the input is already ambiguous. For example:
+// * "refs/heads/the-name" vs "refs/heads/refs/heads/the-name"
+// * "refs/tags/1234567890" vs commit "1234567890"
+// In most cases, it SHOULD AVOID using this function, unless there is an irresistible reason (eg: make API friendly to end users)
+// If the function is used, the caller SHOULD CHECK the ref type carefully.
+func (repo *Repository) UnstableGuessRefByShortName(shortName string) RefName {
+	if repo.IsBranchExist(shortName) {
+		return RefNameFromBranch(shortName)
+	}
+	if repo.IsTagExist(shortName) {
+		return RefNameFromTag(shortName)
+	}
+	if strings.HasPrefix(shortName, "refs/") {
+		if repo.IsReferenceExist(shortName) {
+			return RefName(shortName)
+		}
+	}
+	commit, err := repo.GetCommit(shortName)
+	if err == nil {
+		commitIDString := commit.ID.String()
+		if strings.HasPrefix(commitIDString, shortName) {
+			return RefName(commitIDString)
+		}
+	}
+	return ""
+}