refactor: eliminate duplicate executeChain calls in push approval flow

[fabiovincenzi]

Fixes #1196
Refactor of teeAndValidate middleware to extractRawBody that only extracts request body, centralized all validation logic in proxyFilter function, and eliminated duplicate executeChain() calls for POST git-pack requests

[netlify]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.88%. Comparing base (cbc7ad6) to head (afece3a).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1209      +/-   ##
==========================================
+ Coverage   83.87%   83.88%   +0.01%     
==========================================
  Files          68       68              
  Lines        2908     2904       -4     
  Branches      367      364       -3     
==========================================
- Hits         2439     2436       -3     
  Misses        409      409              
+ Partials       60       59       -1     

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[kriswest]

LGTM - have you tested against any large pushes?

[fabiovincenzi]

LGTM - have you tested against any large pushes?

@kriswest I'm actually doing some manual testing here, the fix successfully eliminates the duplicate executeChain calls - I can see in the logs, which should improve performance.

However, I'm investigating an issue where large pushes seem to hang during the getRawBody() buffering step, both before and after my changes.

[kriswest]

@fabiovincenzi if you end up needing an alternative to raw-body you could try something simple like:

app.use(function(req, res, next) {
  req.rawBody = '';
  req.setEncoding('utf8');

  req.on('data', function(chunk) { 
    req.rawBody += chunk;
  });

  req.on('end', function() {
    next();
  });
});

I can't think what else might be stalling things...

[fabiovincenzi]

@kriswest
The stalling wasn't raw-body itself but the PassThrough stream highWaterMark being too small (16KB default).
Fixed by increasing it to 4MB.
Now handles big pushes as well.

[kriswest]

Aha, good catch then - I think this is possibly affecting us and would explain some weird performance issues

[kriswest]

LGTM