worktree: symlink support

[mcuadros]

Fixes: #358

[ajnavarro]

we are missing the close error.

[ajnavarro]

we are missing the close error.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@3ae5d4d). Click here to learn what that means.
The diff coverage is 69.86%.

@@           Coverage Diff            @@
##             master    #436   +/-   ##
========================================
  Coverage          ?   77.1%           
========================================
  Files             ?     124           
  Lines             ?    9084           
  Branches          ?       0           
========================================
  Hits              ?    7004           
  Misses            ?    1310           
  Partials          ?     770

Impacted Files	Coverage Δ
utils/merkletrie/filesystem/node.go	65.43% <65.21%> (ø)
worktree_commit.go	69.78% <66.66%> (ø)
worktree.go	64.49% <73.33%> (ø)
worktree_status.go	69.47% <76.47%> (ø)

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