ENH: Allow adjusting histogram matching of configuration files

[mgxd]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 69.35%. Comparing base (7bd6a53) to head (69d82d8).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
niworkflows/interfaces/norm.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #911      +/-   ##
==========================================
- Coverage   69.37%   69.35%   -0.03%     
==========================================
  Files          86       86              
  Lines        8468     8472       +4     
  Branches     1057     1058       +1     
==========================================
+ Hits         5875     5876       +1     
- Misses       2370     2373       +3     
  Partials      223      223              

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[effigies]

I'm fine with this. It's backwards-compatible, so could be part of a patch release.