Add suggested changes commit message documentation

This commit adds documentation coverage for the apply
suggested changes custom commit message configuration
and its API counterpart.

doc/api/projects.md

@@ -157,6 +157,7 @@ When the user is authenticated and `simple` is not set this returns something li
     "request_access_enabled": false,
     "merge_method": "merge",
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 37,
       "storage_size": 1038090,
@@ -256,6 +257,7 @@ When the user is authenticated and `simple` is not set this returns something li
     "service_desk_enabled": false,
     "service_desk_address": null,
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 12,
       "storage_size": 2066080,
@@ -388,6 +390,7 @@ This endpoint supports [keyset pagination](README.md#keyset-based-pagination) fo
     "request_access_enabled": false,
     "merge_method": "merge",
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 37,
       "storage_size": 1038090,
@@ -487,6 +490,7 @@ This endpoint supports [keyset pagination](README.md#keyset-based-pagination) fo
     "service_desk_enabled": false,
     "service_desk_address": null,
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 12,
       "storage_size": 2066080,
@@ -598,6 +602,7 @@ Example response:
     "request_access_enabled": false,
     "merge_method": "merge",
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 37,
       "storage_size": 1038090,
@@ -694,6 +699,7 @@ Example response:
     "service_desk_enabled": false,
     "service_desk_address": null,
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "statistics": {
       "commit_count": 12,
       "storage_size": 2066080,
@@ -844,6 +850,7 @@ GET /projects/:id
   "service_desk_enabled": false,
   "service_desk_address": null,
   "autoclose_referenced_issues": true,
+  "suggestion_commit_message": null,
   "statistics": {
     "commit_count": 37,
     "storage_size": 1038090,
@@ -1068,6 +1075,7 @@ POST /projects/user/:user_id
 | `only_allow_merge_if_all_discussions_are_resolved` | boolean | no | Set whether merge requests can only be merged when all the discussions are resolved |
 | `merge_method` | string | no | Set the [merge method](#project-merge-method) used |
 | `autoclose_referenced_issues` | boolean | no | Set whether auto-closing referenced issues on default branch |
+| `suggestion_commit_message` | string | no | The commit message used to apply merge request suggestions |
 | `remove_source_branch_after_merge` | boolean | no | Enable `Delete source branch` option by default for all new merge requests |
 | `lfs_enabled` | boolean | no | Enable LFS |
 | `request_access_enabled` | boolean | no | Allow users to request member access |
@@ -1133,6 +1141,7 @@ PUT /projects/:id
 | `only_allow_merge_if_all_discussions_are_resolved` | boolean | no | Set whether merge requests can only be merged when all the discussions are resolved |
 | `merge_method` | string | no | Set the [merge method](#project-merge-method) used |
 | `autoclose_referenced_issues` | boolean | no | Set whether auto-closing referenced issues on default branch |
+| `suggestion_commit_message` | string | no | The commit message used to apply merge request suggestions |
 | `remove_source_branch_after_merge` | boolean | no | Enable `Delete source branch` option by default for all new merge requests |
 | `lfs_enabled` | boolean | no | Enable LFS |
 | `request_access_enabled` | boolean | no | Allow users to request member access |
@@ -1265,6 +1274,7 @@ Example responses:
     "request_access_enabled": false,
     "merge_method": "merge",
     "autoclose_referenced_issues": true,
+    "suggestion_commit_message": null,
     "_links": {
       "self": "http://example.com/api/v4/projects",
       "issues": "http://example.com/api/v4/projects/1/issues",
@@ -1354,6 +1364,7 @@ Example response:
   "request_access_enabled": false,
   "merge_method": "merge",
   "autoclose_referenced_issues": true,
+  "suggestion_commit_message": null,
   "_links": {
     "self": "http://example.com/api/v4/projects",
     "issues": "http://example.com/api/v4/projects/1/issues",
@@ -1442,6 +1453,7 @@ Example response:
   "request_access_enabled": false,
   "merge_method": "merge",
   "autoclose_referenced_issues": true,
+  "suggestion_commit_message": null,
   "_links": {
     "self": "http://example.com/api/v4/projects",
     "issues": "http://example.com/api/v4/projects/1/issues",
@@ -1617,6 +1629,7 @@ Example response:
   "request_access_enabled": false,
   "merge_method": "merge",
   "autoclose_referenced_issues": true,
+  "suggestion_commit_message": null,
   "_links": {
     "self": "http://example.com/api/v4/projects",
     "issues": "http://example.com/api/v4/projects/1/issues",
@@ -1724,6 +1737,7 @@ Example response:
   "request_access_enabled": false,
   "merge_method": "merge",
   "autoclose_referenced_issues": true,
+  "suggestion_commit_message": null,
   "_links": {
     "self": "http://example.com/api/v4/projects",
     "issues": "http://example.com/api/v4/projects/1/issues",

doc/user/discussions/index.md

@@ -414,9 +414,8 @@ the Merge Request authored by the user that applied them.
 
 Once the author applies a suggestion, it will be marked with the **Applied** label,
 the thread will be automatically resolved, and GitLab will create a new commit
-with the message `Apply suggestion to <file-name>` and push the suggested change
-directly into the codebase in the merge request's branch.
-[Developer permission](../permissions.md) is required to do so.
+and push the suggested change directly into the codebase in the merge request's
+branch. [Developer permission](../permissions.md) is required to do so.
 
 > **Note:**
 Custom commit messages will be introduced by
@@ -444,6 +443,23 @@ Suggestions covering multiple lines are limited to 100 lines _above_ and 100
 lines _below_ the commented diff line, allowing up to 200 changed lines per
 suggestion.
 
+### Configure the commit message for applied suggestions
+
+GitLab will use `Apply suggestion to <file-name>` by default as commit messages
+when applying change suggestions. This commit message can be customized to
+follow any guidelines you might have. To do so, open the **Merge requests** tab
+within your project settings and change the **Merge suggestions** text.
+
+![Suggestion Commit Message Configuration](img/suggestion-commit-message-configuration.png)
+
+You can also use following variables besides static text:
+
+- `%{project_path}`: The full URL safe project path. E.g: *my-group/my-project*
+- `%{project_name}`: The human readable name of the project. E.g: *My Project*
+- `%{file_path}`: The full path of the file the suggestion is applied to. E.g: *docs/index.md*
+- `%{branch_name}`: The name of the branch the suggestion is applied on. E.g: *my-feature-branch*
+- `%{user_name}`: The name of the user applying the suggestion. E.g: *User 1*
+
 ## Start a thread by replying to a standard comment
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/issues/30299) in GitLab 11.9

doc/user/project/settings/index.md

@@ -91,6 +91,7 @@ Set up your project's merge request settings:
 - Enable [merge only if pipeline succeeds](../merge_requests/merge_when_pipeline_succeeds.md).
 - Enable [merge only when all threads are resolved](../../discussions/index.md#only-allow-merge-requests-to-be-merged-if-all-threads-are-resolved).
 - Enable [`delete source branch after merge` option by default](../merge_requests/getting_started.md#deleting-the-source-branch)
+- Configure [suggested changes commit messages](../../discussions/index.md#configure-the-commit-message-for-applied-suggestions)
 
 ![project's merge request settings](img/merge_requests_settings.png)