Fix amending commits whose commit message is empty (#4732)

- **PR Description**

When the commit message is empty, the `--amend` command will produce an error.
Solution: Add the `--allow-empty-message` option.

Author: stefanhaller

pkg/commands/git_commands/commit.go

@@ -23,7 +23,7 @@ func NewCommitCommands(gitCommon *GitCommon) *CommitCommands {
 // ResetAuthor resets the author of the topmost commit
 func (self *CommitCommands) ResetAuthor() error {
 	cmdArgs := NewGitCmd("commit").
-		Arg("--allow-empty", "--only", "--no-edit", "--amend", "--reset-author").
+		Arg("--allow-empty", "--allow-empty-message", "--only", "--no-edit", "--amend", "--reset-author").
 		ToArgv()
 
 	return self.cmd.New(cmdArgs).Run()
@@ -32,7 +32,7 @@ func (self *CommitCommands) ResetAuthor() error {
 // Sets the commit's author to the supplied value. Value is expected to be of the form 'Name <Email>'
 func (self *CommitCommands) SetAuthor(value string) error {
 	cmdArgs := NewGitCmd("commit").
-		Arg("--allow-empty", "--only", "--no-edit", "--amend", "--author="+value).
+		Arg("--allow-empty", "--allow-empty-message", "--only", "--no-edit", "--amend", "--author="+value).
 		ToArgv()
 
 	return self.cmd.New(cmdArgs).Run()
@@ -247,7 +247,7 @@ func (self *CommitCommands) AmendHead() error {
 
 func (self *CommitCommands) AmendHeadCmdObj() *oscommands.CmdObj {
 	cmdArgs := NewGitCmd("commit").
-		Arg("--amend", "--no-edit", "--allow-empty").
+		Arg("--amend", "--no-edit", "--allow-empty", "--allow-empty-message").
 		ToArgv()
 
 	return self.cmd.New(cmdArgs)

pkg/commands/git_commands/rebase_test.go

@@ -141,7 +141,7 @@ func TestRebaseDiscardOldFileChanges(t *testing.T) {
 				ExpectGitArgs([]string{"rebase", "--interactive", "--autostash", "--keep-empty", "--no-autosquash", "--rebase-merges", "abcdef"}, "", nil).
 				ExpectGitArgs([]string{"cat-file", "-e", "HEAD^:test999.txt"}, "", nil).
 				ExpectGitArgs([]string{"checkout", "HEAD^", "--", "test999.txt"}, "", nil).
-				ExpectGitArgs([]string{"commit", "--amend", "--no-edit", "--allow-empty"}, "", nil).
+				ExpectGitArgs([]string{"commit", "--amend", "--no-edit", "--allow-empty", "--allow-empty-message"}, "", nil).
 				ExpectGitArgs([]string{"rebase", "--continue"}, "", nil),
 			test: func(err error) {
 				assert.NoError(t, err)