Make git clone URL could use current signed-in user (#33091)

close #33086

* Add a special value for "SSH_USER" setting: `(DOER_USERNAME)`
* Improve parseRepositoryURL and add tests (now it doesn't have hard
dependency on some setting values)

Many changes are just adding "ctx" and "doer" argument to functions.

By the way, improve app.example.ini, remove all `%(key)s` syntax, it
only makes messy and no user really cares about it.

Document: https://gitea.com/gitea/docs/pulls/138

modules/git/remote.go

@@ -39,7 +39,7 @@ func GetRemoteURL(ctx context.Context, repoPath, remoteName string) (*giturl.Git
 	if err != nil {
 		return nil, err
 	}
-	return giturl.Parse(addr)
+	return giturl.ParseGitURL(addr)
 }
 
 // ErrInvalidCloneAddr represents a "InvalidCloneAddr" kind of error.

modules/git/url/url.go

@@ -21,7 +21,7 @@ func (err ErrWrongURLFormat) Error() string {
 // GitURL represents a git URL
 type GitURL struct {
 	*stdurl.URL
-	extraMark int // 0 no extra 1 scp 2 file path with no prefix
+	extraMark int // 0: standard URL with scheme, 1: scp short syntax (no scheme), 2: file path with no prefix
 }
 
 // String returns the URL's string
@@ -38,8 +38,11 @@ func (u *GitURL) String() string {
 	}
 }
 
-// Parse parse all kinds of git URL
-func Parse(remote string) (*GitURL, error) {
+// ParseGitURL parse all kinds of git URL:
+// * Full URL: http://git@host/path, http://git@host:port/path
+// * SCP short syntax: git@host:/path
+// * File path: /dir/repo/path
+func ParseGitURL(remote string) (*GitURL, error) {
 	if strings.Contains(remote, "://") {
 		u, err := stdurl.Parse(remote)
 		if err != nil {

modules/git/url/url_test.go

@@ -157,7 +157,7 @@ func TestParseGitURLs(t *testing.T) {
 
 	for _, kase := range kases {
 		t.Run(kase.kase, func(t *testing.T) {
-			u, err := Parse(kase.kase)
+			u, err := ParseGitURL(kase.kase)
 			assert.NoError(t, err)
 			assert.EqualValues(t, kase.expected.extraMark, u.extraMark)
 			assert.EqualValues(t, *kase.expected, *u)