tweak the behavior of the `hash` column in the `refs` table when dealing with `tags`

[patrickdevivo]

if the ref is an annotated tag, output the hash of the object it is pointing to instead of its own hash. This makes it easier to deal with lightweight and annotated tags when querying the refs table, as the hash column will always point to a commit (and can be joined with the commits table)

@riyaz-ali what do you think? Is this weird to do?

The purpose would be such that

SELECT * FROM refs JOIN commits USING(hash)
WHERE type = 'tag'

Would work for both annotated and lightweight tags, where now it only works for lightweight

[codecov-commenter]

Codecov Report

Merging #217 (6144fe8) into main (0407ab9) will decrease coverage by 0.05%. The diff coverage is 57.14%.

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
- Coverage   69.82%   69.76%   -0.06%     
==========================================
  Files          47       47              
  Lines        2505     2510       +5     
==========================================
+ Hits         1749     1751       +2     
- Misses        481      482       +1     
- Partials      275      277       +2     

Impacted Files	Coverage Δ
extensions/internal/git/refs.go	73.11% <57.14%> (-1.89%)	:arrow_down:

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[riyaz-ali]

The change looks good, but how will one fetch the hash of the tag object if they need to?

[riyaz-ali]

Also, there's a COMMIT_FROM_TAG scalar function that gives you the hash of the commit pointed to by the tag. I believe you can combine that with CASE...WHEN to achieve the same result?

The function referred can be found at extensions/git/internal/refs_func.go