Better end user visibility for failures in agit PRs

[TheFox0x7]

Feature Description

The error messages in agit PRs aren't very visible to the end user. I think that adding an error label for fails would make them pop out more (if one has color enabled). See screenshots for full options.

I encountered this while trying to submit an agit PR to docs, which uncovered a missing UserMsg, which would've been helpful:

gitea/routers/private/hook_proc_receive.go

Lines 31 to 34 in 7553ae1

	log.Error(err.Error())
	ctx.JSON(http.StatusInternalServerError, private.Response{
	Err: err.Error(),
	})

and I've glanced over it before, so I think having a color before it would be helpful.

Similarly an instruction for setting up branch tracking would be a good improvement - no idea how to set it up though.

Screenshots

Possible options:

[lunny]

I resolve the problems via resync of all git hooks because there are no proc-receive hooks under this repository. I think there is no migration for git hooks when introducing the agit feature.

[TheFox0x7]

I can reproduce this (or similar) fault locally - lack of collaborator status prevents user from submitting agit PR, which is not forwarded to them:

remote: Gitea: Internal Server Error (no message for end users)
remote: error: proc-receive exited abnormally

I in the original text I meant that the error should be made more visible (and descriptive), which I figured is more of a enhancement that an a bug. Some errors - like the lack of collaborator status - are worth forwarding to user in my opinion.
Apologies if I worded it in a confusing way originally.

[wxiaoguang]

If I understand correctly , only the "Gitea:" prefixed line is outputed by Gitea.

Other lines are from git, which are not controllable