Fix ref parsing in commit messages

[ethantkoenig]

Fix bug where commit messages containing /# would cause an error, and the rest of the commit message would not be parsed for issue references. This is because GetIndexByRef would return ErrInvalidReference when it encountered /#.

This PR also

• Improves the regexps for issue refs to avoid superfluous matches (issueReferenceKeywordsPat previously matched every word!)
• Refactor common code so that it can be reused
• Adds unit tests for commit message parsing

[lafriks]

Tests seems to be failing

[codecov-io]

Codecov Report

Merging #3067 into master will increase coverage by 0.02%.
The diff coverage is 65.11%.

@@            Coverage Diff             @@
##           master    #3067      +/-   ##
==========================================
+ Coverage   33.45%   33.48%   +0.02%     
==========================================
  Files         270      270              
  Lines       39553    39534      -19     
==========================================
+ Hits        13232    13236       +4     
+ Misses      24429    24412      -17     
+ Partials     1892     1886       -6

Impacted Files	Coverage Δ
models/issue.go	45.24% <ø> (+0.41%)	⬆️
models/action.go	65.04% <65.11%> (+1.24%)	⬆️
modules/indexer/repo.go	60.86% <0%> (-2.61%)	⬇️
models/repo_indexer.go	50.99% <0%> (-1%)	⬇️
models/repo.go	38.26% <0%> (+0.3%)	⬆️
modules/process/manager.go	81.15% <0%> (+4.34%)	⬆️

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[lafriks]

LGTM

[lunny]

LGTM

[lunny]

make L-G-T-M work