make commit message template ignore commented lines

[annthurium]

Description of the Change

This change fixes a bug where commit message templates that include commented lines were included in the body of the commit.

If a commit template exists, istrip commented lines from the commit message.

Alternate Designs

• My initial approach had us ignoring the verbatim flag if a commit template was present. However, we want to preserve the verbatim flag because otherwise commits made from the mini editor might be formatted weirdly in some cases. See Revisit commit message processing #1500 for more info.

• We discussed ripping out the verbatim flag entirely, to aid complexity, but wanted to maintain the hard wrapping so as not to break formatting for users who are using the mini editor but not using a template.

Benefits

• Users can make commits with message templates, without including commented lines in the commit output, because probably they do not want that.
• Consistent with command line git behavior

Possible Drawbacks

• Adds more complexity to some code that's already rife with special cases.
• There might be some users who have commit templates and want to keep lines that start with #

Applicable Issues

#1817

Metrics

N/A

Tests

• Manually tested making a commit with a commit template set, where the template included # characters. Verified that those commented lines did not show up when using git log to inspect the commit.
• unit test in git-shell-out-strategy to verify that commented lines are stripped when using commit message templates. (We already have a unit test for validating that commented lines are not stripped, if a commit template does not exist.)

Documentation

Added some code comments.

Release Notes

Fixed an issue where commits made with commit message templates were not stripping comment characters.

[codecov]

Codecov Report

Merging #1902 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1902      +/-   ##
==========================================
- Coverage   91.09%   91.08%   -0.02%     
==========================================
  Files         185      185              
  Lines       10719    10722       +3     
  Branches     1575     1576       +1     
==========================================
+ Hits         9765     9766       +1     
- Misses        954      956       +2

Impacted Files	Coverage Δ
lib/git-shell-out-strategy.js	87.58% <100%> (+0.06%)	⬆️
lib/models/repository-states/present.js	95.02% <0%> (-0.39%)	⬇️

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[kuychaco]

Looks good to me! 👍