Improve the Repository files documentation

Signed-off-by: Rémy Coutable <remy@rymai.me>

doc/api/repository_files.md

@@ -97,7 +97,10 @@ POST /projects/:id/repository/files/:file_path
 ```
 
 ```bash
-curl --request POST --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fprojectrb%2E?branch=master&author_email=author%40example.com&author_name=Firstname%20Lastname&content=some%20content&commit_message=create%20a%20new%20file'
+curl --request POST --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' --header "Content-Type: application/json" \
+  --data '{"branch": "master", "author_email": "author@example.com", "author_name": "Firstname Lastname", \
+    "content": "some content", "commit_message": "create a new file"}' \
+  'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fproject%2Erb'
 ```
 
 Example response:
@@ -129,7 +132,10 @@ PUT /projects/:id/repository/files/:file_path
 ```
 
 ```bash
-curl --request PUT --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fproject%2Erb?branch=master&author_email=author%40example.com&author_name=Firstname%20Lastname&content=some%20other%20content&commit_message=update%20file'
+curl --request PUT --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' --header "Content-Type: application/json" \
+  --data '{"branch": "master", "author_email": "author@example.com", "author_name": "Firstname Lastname", \
+    "content": "some content", "commit_message": "update file"}' \
+  'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fproject%2Erb'
 ```
 
 Example response:
@@ -171,7 +177,10 @@ DELETE /projects/:id/repository/files/:file_path
 ```
 
 ```bash
-curl --request DELETE --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' 'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fproject%2Erb?branch=master&author_email=author%40example.com&author_name=Firstname%20Lastname&commit_message=delete%20file'
+curl --request DELETE --header 'PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK' --header "Content-Type: application/json" \
+  --data '{"branch": "master", "author_email": "author@example.com", "author_name": "Firstname Lastname", \
+    "commit_message": "delete file"}' \
+  'https://gitlab.example.com/api/v4/projects/13083/repository/files/app%2Fproject%2Erb'
 ```
 
 Parameters: