CODEWITHSUNDEEP
gitgit-diff
Barry
Barry

Reputation: 302643

What is the difference between these git diff commands?

I am on a branch, br, which is pushed as origin/br, on which I've made several several commits. In the case where HEAD == br == origin/br, I am running these two commands:

(1) git diff <some-commit>

and

(2) git diff <some-commit> HEAD origin/br

where HEAD is a direct descendant from <some-commit>

The two give different results, and while I understand that what (1) does I have no idea what (2) is printing. What does (2) do? I believe it has something to do with this entry from the man page, but I do not know what it means:

   <path>...
       The <paths> parameters, when given, are used to limit the diff to the named 
       paths (you can give directory names and get diff for all files under
       them).

Upvotes: 1

Views: 211

Answers (1)

jthill
jthill

Reputation: 60235

I'm betting the output is showing you diff -cc $pathname and index $sha1,$sha2..$sha3 where sometimes two of sha's 1,2,3 are the same, and from some quick digging I think git's probably treating one of the commits (the middle, it looks like) as an explicit merge base, the other two as explicit merge tips -- but according to this from builtin/diff.c the arguments you're passing are not correct.

/*
 * We could get N tree-ish in the rev.pending_objects list.
 * Also there could be M blobs there, and P pathspecs.
 *
 * N=0, M=0:
 *  cache vs files (diff-files)
 * N=0, M=2:
 *      compare two random blobs.  P must be zero.
 * N=0, M=1, P=1:
 *  compare a blob with a working tree file.
 *
 * N=1, M=0:
 *      tree vs cache (diff-index --cached)
 *
 * N=2, M=0:
 *      tree vs tree (diff-tree)
 *
 * N=0, M=0, P=2:
 *      compare two filesystem entities (aka --no-index).
 *
 * Other cases are errors.
 */

Upvotes: 1

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