Make manual merge autodetection optional and add manual merge as merge method (#12543)

* Make auto check manual merge as a chooseable mod and add manual merge way on ui

as title, Before this pr, we use same way with GH to check manually merge.
It good, but in some special cases, misjudgments can occur. and it's hard
to fix this bug. So I add option to allow repo manager block "auto check manual merge"
function, Then it will have same style like gitlab(allow empty pr). and to compensate for
not being able to detect THE PR merge automatically, I added a manual approach.

Signed-off-by: a1012112796 <1012112796@qq.com>

* make swager

* api support

* ping ci

* fix TestPullCreate_EmptyChangesWithCommits

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* Apply review suggestions and add test

* Apply suggestions from code review

Co-authored-by: zeripath <art27@cantab.net>

* fix build

* test error message

* make fmt

* Fix indentation issues identified by @silverwind

Co-authored-by: silverwind <me@silverwind.io>

* Fix tests and make manually merged disabled error on API the same

Signed-off-by: Andrew Thornton <art27@cantab.net>

* a small nit

* fix wrong commit id error

* fix bug

* simple test

* fix test

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

options/locale/locale_en-US.ini

@@ -1105,6 +1105,7 @@ issues.context.delete = Delete
 issues.no_content = There is no content yet.
 issues.close_issue = Close
 issues.pull_merged_at = `merged commit <a href="%[1]s">%[2]s</a> into <b>%[3]s</b> %[4]s`
+issues.manually_pull_merged_at = `merged commit <a href="%[1]s">%[2]s</a> into <b>%[3]s</b> %[4]s manually`
 issues.close_comment_issue = Comment and Close
 issues.reopen_issue = Reopen
 issues.reopen_comment_issue = Comment and Reopen
@@ -1273,6 +1274,7 @@ pulls.compare_compare = pull from
 pulls.filter_branch = Filter branch
 pulls.no_results = No results found.
 pulls.nothing_to_compare = These branches are equal. There is no need to create a pull request.
+pulls.nothing_to_compare_and_allow_empty_pr = These branches are equal. This PR will be empty.
 pulls.has_pull_request = `A pull request between these branches already exists: <a href="%[1]s/pulls/%[3]d">%[2]s#%[3]d</a>`
 pulls.create = Create Pull Request
 pulls.title_desc = wants to merge %[1]d commits from <code>%[2]s</code> into <code id="branch_target">%[3]s</code>
@@ -1285,6 +1287,8 @@ pulls.reopen_to_merge = Please reopen this pull request to perform a merge.
 pulls.cant_reopen_deleted_branch = This pull request cannot be reopened because the branch was deleted.
 pulls.merged = Merged
 pulls.merged_as = The pull request has been merged as <a rel="nofollow" class="ui sha" href="%[1]s"><code>%[2]s</code></a>.
+pulls.manually_merged = Manually merged
+pulls.manually_merged_as = The pull request has been manually merged as <a rel="nofollow" class="ui sha" href="%[1]s"><code>%[2]s</code></a>.
 pulls.is_closed = The pull request has been closed.
 pulls.has_merged = The pull request has been merged.
 pulls.title_wip_desc = `<a href="#">Start the title with <strong>%s</strong></a> to prevent the pull request from being merged accidentally.`
@@ -1292,6 +1296,7 @@ pulls.cannot_merge_work_in_progress = This pull request is marked as a work in p
 pulls.data_broken = This pull request is broken due to missing fork information.
 pulls.files_conflicted = This pull request has changes conflicting with the target branch.
 pulls.is_checking = "Merge conflict checking is in progress. Try again in few moments."
+pulls.is_empty = "This branch is equal with the target branch."
 pulls.required_status_check_failed = Some required checks were not successful.
 pulls.required_status_check_missing = Some required checks are missing.
 pulls.required_status_check_administrator = As an administrator, you may still merge this pull request.
@@ -1312,6 +1317,7 @@ pulls.reject_count_1 = "%d change request"
 pulls.reject_count_n = "%d change requests"
 pulls.waiting_count_1 = "%d waiting review"
 pulls.waiting_count_n = "%d waiting reviews"
+pulls.wrong_commit_id = "commit id must be a commit id on the target branch"
 
 pulls.no_merge_desc = This pull request cannot be merged because all repository merge options are disabled.
 pulls.no_merge_helper = Enable merge options in the repository settings or merge the pull request manually.
@@ -1322,6 +1328,8 @@ pulls.merge_pull_request = Merge Pull Request
 pulls.rebase_merge_pull_request = Rebase and Merge
 pulls.rebase_merge_commit_pull_request = Rebase and Merge (--no-ff)
 pulls.squash_merge_pull_request = Squash and Merge
+pulls.merge_manually = Manually merged
+pulls.merge_commit_id = The merge commit ID
 pulls.require_signed_wont_sign = The branch requires signed commits but this merge will not be signed
 pulls.invalid_merge_option = You cannot use this merge option for this pull request.
 pulls.merge_conflict = Merge Failed: There was a conflict whilst merging. Hint: Try a different strategy
@@ -1545,6 +1553,8 @@ settings.pulls.allow_merge_commits = Enable Commit Merging
 settings.pulls.allow_rebase_merge = Enable Rebasing to Merge Commits
 settings.pulls.allow_rebase_merge_commit = Enable Rebasing with explicit merge commits (--no-ff)
 settings.pulls.allow_squash_commits = Enable Squashing to Merge Commits
+settings.pulls.allow_manual_merge = Enable Mark PR as manually merged
+settings.pulls.enable_autodetect_manual_merge = Enable autodetect manual merge (Note: In some special cases, misjudgments can occur)
 settings.projects_desc = Enable Repository Projects
 settings.admin_settings = Administrator Settings
 settings.admin_enable_health_check = Enable Repository Health Checks (git fsck)