fix: use full relative path for dir filter and only traverse match

[noahnu]

Addresses: https://github.com/tophat/codewatch/issues/77

Two changes, both breaking changes:

• directory_filter now receives full path of directory relative to base directory. Previously, it only received the directory basename.
• FileWalker will no longer traverse subdirectories that do not match the directory_filter. Previously, it traversed all directories.

One of the issues with the old behaviour:

• A directory_filter with return _dir != '.git' would still traverse the entire .git directory tree. Although it wouldn't attempt to parse these files b/c the file_filter defaults to only look at ".py", it would still have to test the path. This adds an extreme performance overhead to running codewatch on even a moderately large directory tree.

Tests

Updated test_it_filters_on_directories to be stronger. It now tests using the full relative path "./dir2" rather than just a substring match. Since dir2_subdir will not match "./dir2", the test must be passing b/c the directory walker is successfully pruning the dir2 folder. Had to update the mock walker to actually work like the real os walk function (i.e. rely on a mutable directory list).

[codecov[bot]]

Codecov Report

Merging #94 into master will decrease coverage by 0.04%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #94      +/-   ##
==========================================
- Coverage   93.48%   93.43%   -0.05%     
==========================================
  Files          10       10              
  Lines         399      396       -3     
  Branches       57       57              
==========================================
- Hits          373      370       -3     
  Misses         15       15              
  Partials       11       11

Flag	Coverage Δ
#py27	93.43% <100%> (-0.05%)	:arrow_down:
#py36	93.43% <100%> (-0.05%)	:arrow_down:
#py37	93.43% <100%> (-0.05%)	:arrow_down:

Impacted Files	Coverage Δ
codewatch/file_walker.py	100% <100%> (ø)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 6aef223...c79a215. Read the comment docs.

[noahnu]

Updated directory filter test and mock walker.