Edit executable bit from Web UI
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### Description
If you start a new repo, add a deploy key and add a shell script, you're going to have a bad time.
Once you use the deploy key (read-only) to pull the shell script, you wont be able to execute it, because
there is no way to edit modes in the web ui, specially the executable bit.
### Proposal
Edit executable bit from Web UI
### Links / references
https://gitlab.uservoice.com/forums/176466-deprecated-feedback-forum/suggestions/6719766-edit-executable-bit-from-web-ui
#### Overview
Why should someone use this feature?
Laziness
#### Use cases
Everyone who has ever needed to use the Web UI to edit a *nix executable.
### Feature checklist
issue