Cache source packages when reference/revision is available

[adduc]

Fixes #366

For projects that use specific revisions for packages (e.g. if a bug fix has not made it to a tagged release yet), the PHP language server would reparse the package's files every time the server started, even if the package had not changed. This change introduces caching support for packages that are checked out from source, by using the revision as part of the cache key.

[codecov]

Codecov Report

Merging #367 into master will increase coverage by 2.61%.
The diff coverage is 37.5%.

@@             Coverage Diff              @@
##             master     #367      +/-   ##
============================================
+ Coverage     84.33%   86.95%   +2.61%     
- Complexity      834      835       +1     
============================================
  Files            59       59              
  Lines          1724     1732       +8     
============================================
+ Hits           1454     1506      +52     
+ Misses          270      226      -44

Impacted Files	Coverage Δ	Complexity Δ
src/Indexer.php	91.25% <37.5%> (+28.23%)	19 <0> (+1)	⬆️
src/Index/ProjectIndex.php	100% <0%> (ø)	4% <0%> (ø)	⬇️
src/LanguageServer.php	95.18% <0%> (+2.4%)	20% <0%> (ø)	⬇️
src/Index/Index.php	80.39% <0%> (+11.76%)	21% <0%> (ø)	⬇️
src/Index/DependenciesIndex.php	53.33% <0%> (+40%)	6% <0%> (ø)	⬇️
src/Cache/FileSystemCache.php	70% <0%> (+50%)	8% <0%> (ø)	⬇️

[adduc]

Regarding testing for this change, I'm still wrapping my head around the code. I think it can be accomplished by including a composer.json and composer.lock within fixtures to mock a faux install. I'm going to look into this further.

[felixfbecker]

package name is checked in both conditions

[felixfbecker]

space between else if

[felixfbecker]

LGTM overall.
Testing with a fake composer.json and composer.lock sounds like a good approach. Ideally this would be a unit test for the Indexer that asserts a stubbed Cache is called

[adduc]

I've made changes based off your feedback, and modified tests for the two current package caching strategies.

I think this is ready for another review.

[felixfbecker]

Could you do the tests as a unit test for the Indexer?

[adduc]

I'd be willing to give it a shot.

[umpirsky]

Any updates on this?