[GITEA] Allow user to select email for file operations in Web UI

- Add a dropdown to the web interface for changing files to select which
Email should be used for the commit. It only shows (and verifies) that a
activated mail can be used, while this isn't necessary, it's better to
have this already in place.
- Added integration testing.
- Resolves https://codeberg.org/forgejo/forgejo/issues/281

(cherry picked from commit 564e701f40)
(cherry picked from commit de8f2e03cc)
(cherry picked from commit 0182cff12e)
(cherry picked from commit 9c74254d46)

services/repository/files/file.go

@@ -123,6 +123,8 @@ func GetAuthorAndCommitterUsers(author, committer *IdentityOptions, doer *user_m
 			if committer.Name != "" {
 				committerUser.FullName = committer.Name
 			}
+			// Use the provided email and not revert to placeholder mail.
+			committerUser.KeepEmailPrivate = false
 		} else {
 			committerUser = &user_model.User{
 				FullName: committer.Name,
@@ -136,6 +138,8 @@ func GetAuthorAndCommitterUsers(author, committer *IdentityOptions, doer *user_m
 			if authorUser.Name != "" {
 				authorUser.FullName = author.Name
 			}
+			// Use the provided email and not revert to placeholder mail.
+			authorUser.KeepEmailPrivate = false
 		} else {
 			authorUser = &user_model.User{
 				FullName: author.Name,