repository: Resolve commit when cloning annotated tag, fixes #557

[orirawlings]

Fixes #557

[orirawlings]

Tests are pending still, but wanted to make sure my general approach made sense. I still have to dig into how the current tests for the repository Clone* methods are implemented.

[orirawlings]

Whoops. Forgot to extract an error constant here.

[codecov]

Codecov Report

Merging #558 into master will decrease coverage by 0.65%.
The diff coverage is 67.74%.

@@            Coverage Diff             @@
##           master     #558      +/-   ##
==========================================
- Coverage    78.1%   77.44%   -0.66%     
==========================================
  Files         129      129              
  Lines        9807     9827      +20     
==========================================
- Hits         7660     7611      -49     
- Misses       1316     1394      +78     
+ Partials      831      822       -9

Impacted Files	Coverage Δ
repository.go	73.71% <67.74%> (-1.02%)	⬇️
plumbing/transport/ssh/common.go	20.54% <0%> (-45.21%)	⬇️
plumbing/transport/ssh/auth_method.go	31.57% <0%> (-22.81%)	⬇️

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[orirawlings]

I've added a failing test. My current strategy prevents an error from occurring, but it leaves the HEAD ref pointed to the tag object rather the underlying commit object. Standard git tooling leaves the HEAD ref pointed at the commit. I'll continue working on this fix.

[orirawlings]

I fixed the PR to ensure that the HEAD ref is left pointing to the commit object.