lookupkey: Added --ref option

Sponsored-by: Joshua Antonishen on Patreon

doc/git-annex-get/comment_2_ce5c85afa01019afe58c79df151c65ff._comment

@@ -0,0 +1,12 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""Re: get file by branch and path in bare repository"""
+ date="2023-09-12T16:46:55Z"
+ content="""
+--branch is limited to a treeish, so not a single file.
+
+You can use `git-annex lookupkey --ref` to look up the key used by a ref to
+a file, and then pass that to `git-annex get --key`
+
+(That's a new feature I added due to you asking this question.)
+"""]]

doc/git-annex-lookupkey.mdwn

@@ -15,6 +15,13 @@ nothing is output, and it exits nonzero.
 
 # OPTIONS
 
+* `--ref`
+
+  Rather than looking for the specified files in the index, interpet them
+  as git refs. For example to find the key used for somefile in tag v1.0:
+
+    git-annex lookupkey v1.0:somefile
+
 * `--batch`
 
   Enable batch mode, in which a line containing the filename is read from