Now you can create a new file and select a target_branch != source_branch.
If the file that you want to create already exists on the target branch an error message is shown
A glDropdown is used to select and create a new branch instead of a text field.

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Reason for renaming is to comply with naming convention of services in
codebase.

Fix information disclosure in `Projects::BlobController#update`

It was possible to discover private project names by modifying `from_merge_request`parameter in `Projects::BlobController#update`. This fixes that.

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

https://gitlab.com/gitlab-org/gitlab-ce/issues/22869

See merge request !2023

Right now, the following naming scheme for diff files is used: diff-1, diff-2, ... and also we have "internal" format which is file-path-HASH, where HASH is sha1 of file path.
Besides, we have HASH_lineA_lineB format to link exact line number in MR diff. It makes sence to unify the way we link diff from outside, while leave "file-path-HASH" format for internal (js) usage.
Changes in this commit  allow to link diff just by HASH, if we don't want specify exact lines, also it changes "file-path-HASH" and "diff-NUMBER" links in code to this unified format.

Inspired by #24010 and !7298

refactors update file

Currently when a user performs an update of a file through the UI  and there
has already been a change committed to the file the previous commits will be
overwritten without a check to see if the file has been changed.

This commit uses the last commit sha at the time the user starts editing the
file and compares it with the current sha of the file being edited to ensure
they are the same before committing the file. If the shas do not match we
throw an exception preventing the commit from the commit from occurring.

Fixes #5857

changes the usasge of path to file_path on blob_controller for compatibillity with the create action

changes the usasge of path to file_path on blob_controller for compatibillity with the create action