Add the option to automatically unlock a repo after a plan has been run

[gezb]

This new option is designed to be used when apply is disabled, there is no reason to hold a lock/plan in this configuration

[codecov]

Codecov Report

Merging #1258 (bafcaa1) into master (1513ee6) will decrease coverage by 0.05%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master    #1258      +/-   ##
==========================================
- Coverage   70.01%   69.95%   -0.06%     
==========================================
  Files          74       74              
  Lines        5556     5562       +6     
==========================================
+ Hits         3890     3891       +1     
- Misses       1307     1311       +4     
- Partials      359      360       +1     

Impacted Files	Coverage Δ
cmd/server.go	79.09% <ø> (ø)
server/events/command_runner.go	50.00% <0.00%> (-0.88%)	⬇️
server/events/comment_parser.go	93.98% <ø> (ø)
server/user_config.go	100.00% <ø> (ø)
server/server.go	62.34% <100.00%> (+0.09%)	⬆️

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[kevincox]

What is the point of locking at all if you are just going to unlock afterwards?

[gezb]

My thoughts were it prevents Atlantis running two plans on the same repo at the same time e.g, two pull requests come in around the same time so trigger an plans

[kevincox]

Terraform already has locking for this built in. By default the second plan will wait for the first. (You can configure the timeout). It seems that this just pessimizes the regular terraform locking.

[jamengual]

when multiple people work on the same repo on different PRs it is pretty annoying when you run a plan and atlantis is locking the whole repo indefinite instead of releasing the lock after plan, so I see how this could help on that case.

not all the plans end up being applied so this could be useful and the only way I know to get around this is to close the PR so another PR can do plan, which is less than ideal and is not related to Terraform remote state locking directly.

done by mistake

[gezb]

I have rebased to see if that fixes the website link test that had failed, I can't see how fixing a typo in the docs would have broken that otherwise

[gezb]

Closing replaced by #1340