fix(compiler): add commit field to compiler engine to handle file type template lite compilation

[ecrupper]

When using any compiler function which does not involve instantiating the compiler with a build (compiler.FromContext(c).WithBuild(b)), any time a lite compilation is requested (many pipeline API endpoints), the compiler fails to grab the correct template from the SCM due to this line. This change addresses the bug by adding a commit field to the compiler engine, which felt like the least invasive way of holding the commit SHA during compilation / template fetching. Open to other ideas as well.

Steps to recreate bug if interested:

1. define a pipeline that calls a template of the file type on the default branch of a repository
2. checkout a new branch, edit the template that is called
3. run pipeline
4. build will compile and run as expected, but requesting {{ base_url }}/api/v1/pipelines/{{ org }}/{{ repo }}/{{ pipeline }}/expand will show you the expanded version as pulling in the template version from the default branch.

[codecov]

Codecov Report

Merging #859 (c26967b) into main (afd00ce) will decrease coverage by 0.01%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             main     #859      +/-   ##
==========================================
- Coverage   66.78%   66.78%   -0.01%     
==========================================
  Files         283      283              
  Lines       14120    14129       +9     
==========================================
+ Hits         9430     9436       +6     
- Misses       4244     4247       +3     
  Partials      446      446              

Impacted Files	Coverage Δ
api/build.go	1.34% <0.00%> (-0.01%)	⬇️
api/webhook.go	0.00% <0.00%> (ø)
compiler/native/expand.go	72.41% <100.00%> (ø)
compiler/native/native.go	85.26% <100.00%> (+0.81%)	⬆️
router/middleware/pipeline/pipeline.go	77.77% <100.00%> (+0.35%)	⬆️

[cognifloyd]

Makes sense to me.

[wass3rw3rk]

let's go to the moon