Andy Whitcroft [off-list ref] writes:
quoted
+For a more complete list of ways to spell object names, see
+"SPECIFYING REVISIONS" section in gitlink:git-rev-parse[1].
+
That section seems to have more compresensive descriptions of the
various definitions of commit-ish, but not a tree-ish. Specifically,
there is no mentions of tree-ish:file
164 * A suffix ':' followed by a path; this names the blob or tree
165 at the given path in the tree-ish object named by the part
166 before the colon.