Support regexp in command builder on the project name

[bewie]

Related to #1288, this PR adds support of regexp on atlantis plan/apply with -p flag.
The main objective is to be able to trigger apply only on a specific range of projects in one GitHub comment.

For Example, all projects that matching my naming convention for staging :

atlantis apply -p .*_staging

Or a specific range of project :

atlantis plan -p project[1-4]

This feature can be enabled with --enable-regexp-cmd flag (disable by default)

Closes #254

[codecov]

Codecov Report

Merging #1419 (90d2529) into master (471646b) will decrease coverage by 0.00%.
The diff coverage is 82.69%.

@@            Coverage Diff             @@
##           master    #1419      +/-   ##
==========================================
- Coverage   69.53%   69.52%   -0.01%     
==========================================
  Files          93       93              
  Lines        6299     6327      +28     
==========================================
+ Hits         4380     4399      +19     
- Misses       1542     1550       +8     
- Partials      377      378       +1     

Impacted Files	Coverage Δ
cmd/server.go	79.09% <ø> (ø)
server/events/yaml/valid/repo_cfg.go	9.09% <0.00%> (-2.03%)	⬇️
server/user_config.go	100.00% <ø> (ø)
server/events/project_command_builder.go	82.30% <93.33%> (+0.29%)	⬆️
server/server.go	64.98% <100.00%> (+0.07%)	⬆️

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[nishkrishnan]

LGTM

[nishkrishnan]

Just realized one thing that becomes a bit confusing. --disable-apply-all doesn't work anymore because theoretically you can just do atlantis apply -p * to circumvent it.

Can you think of a good way to make this more restrictive? Maybe gating this feature with a server flag would be enough?

Thought of a problem

[bewie]

Good point, I guess put this feature behind a server flag is a good idea.

[bewie]

Just realized one thing that becomes a bit confusing. --disable-apply-all doesn't work anymore because theoretically you can just do atlantis apply -p * to circumvent it.

Can you think of a good way to make this more restrictive? Maybe gating this feature with a server flag would be enough?

This feature is now disabled by default and managed by the --enable-regexp-cmd option.

[nishkrishnan]

LGTM

[nishkrishnan]

@bewie before I merge this, can you either update this one with docs on the new flag (and specifically call out that it's not meant to be used with disable-apply-all) or create a new PR for this?

[bewie]

@nishkrishnan I updated the docs, let me know if it looks good to you.