Add option to disable automatic mirror syncing.

[cez81]

Setting the interval to 0 will disable to automatic syncing.

Closes #3562

[codecov-io]

Codecov Report

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The diff coverage is 0%.

@@            Coverage Diff            @@
##             master    #5242   +/-   ##
=========================================
  Coverage          ?   37.37%           
=========================================
  Files             ?      312           
  Lines             ?    46322           
  Branches          ?        0           
=========================================
  Hits              ?    17314           
  Misses            ?    26527           
  Partials          ?     2481

Impacted Files	Coverage Δ
models/repo_mirror.go	2.57% <0%> (ø)
routers/repo/setting.go	10.97% <0%> (ø)

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[zeripath]

hmm... why not just set the mirror interval to blank to disable automatic sync?

[lafriks]

@zeripath because it is number and can not be empty, imho

[zeripath]

Ah but it's not a number - It's an interval 😉 . You have units.

By using 0 to mean never you're breaking the semantics of the interval - 0 could easily mean always, once, never. A blank field is clearly not a valid interval. If there are other uses of an essentially nonsense number being used as flag in the UI - it's ok to add another, but it's a very C way doing things.

BTW are there any limits on how often a mirroring can take place, e.g. should we really be able to set this to 1s? (Edit: stupid me of course there's a minimal interval it's even in the diffs)

[lafriks]

@zeripath but in the end interval is still converted to number of seconds (golang variable is number so it can not contain anything fancy :) )

[zeripath]

Ah, I see - using 0 makes the minimal change to the codebase.

Sorry, I was coming at it from a UI view. Exposing the 0 semantics doesn't make for the nicest UI - but it could be improved later with a little switch that says autosynchronize on/off and the interval box - requiring a non-zero value if on.

I'll lgtm this though in the meantime from a point of view that it works, is simple and can be improved later.