[SOLVED] Are "dangling" and "loose" objects the same?

Are "dangling" and "loose" objects the same?

Git's fsck doc talks about "dangling" objects, while the gc doc talks only about "loose objects". There's a strict split.

But while skimming a few related SO posts, the terms seem to be used interchangeably. In the Git Book v2 and Git's source code as well:

   (main) $ git checkout v2.33.0
(225bc32) $ rg 'dangling (object|commit|blob|tag|tree)' | wc -l
      31
(225bc32) $ rg 'loose (object|commit|blob|tag|tree)' | wc -l
     117

Lastly, both commands are often used in sequence, and it seems clear to me from their behavior that they target the same things.

Thus, "dangling" and "loose" are just 2 similar terms for the same concept. Is this summary correct?

Or is "loose objects" rather a category, while "dangling" is reserved intentionally for the specific types of objects?

Solution

Loose objects - are those that aren't packed. Git can compress many loose objects into a single pack file.
Dangling object - is the one that's not referenced by anything (e.g. an orphan commit which has no branch/tag pointing to it). It's garbage that will at some point be collected by GC.
"Unreachable" object (see comment by @torek). If commit A is a parent of B, then A is not dangling even if B is. Instead A is "unreachable". It's also part of garbage.

Loose object can be dangling, packs can contain dangling objects. So these concepts are orthogonal. But you can create a reference (branch, tag) which will reference a dangling commit and it will stop "dangle".