Re: [PATCH v2 2/2] grep: use '/' delimiter for paths

[Junio C Hamano <gitster@pobox.com>]

Stefan Hajnoczi <stefanha@redhat.com> writes:

> Perhaps it's better to leave this than to merge code that doesn't work
> correctly 100% of the time.

I am not sure if you are shooting for is "work correctly" to begin
with, to be honest.  The current code always shows the "correct"
output which is "the tree-ish object name (expressed in a way easier
to understand by the humans), followed by a colon, followed by the
path in the tree-ish the hit lies".  You are making it "incorrect
but often more convenient", and sometimes that is a worth goal, but
for the particular use cases you presented, i.e.

    $ git grep -e "$pattern" "$commit:path"

a more natural way to express "I want to find this pattern in the
commit under that path" exists:

    $ git grep -e "$pattern" "$commit" -- path

and because of that, I do not think the former form of the query
should happen _less_ often in the first place, which would make it
"incorrect but more convenient if the user gives an unusual query".

So I am not sure if the change to "grep" is worth it.

Having said that, I actually think "make it more convenient" without
making anything incorrect would be to teach the revision parser to
understand

    <any-expression-to-name-a-tree-ish:<path>

as an extended SHA-1 expression to name the blob or the tree at that
path in the tree-ish, e.g. if we can make the revision parser to
take this

    master:Documentation:git.txt

as the name of the blob object, then the current output is both
correct and more convenient.  After all, this sample string starts
at "master:Documentation" (which is an extended SHA-1 expression to
name a tree-ish), followed by a colon, then followed by the path
"git.txt" in it, and "grep -e pattern master:Documentation" would
show hits in that blob prefixed with it.

I.e.

	T=$(git rev-parse master:Documentation)
	git cat-file blob $T:git.txt

would give you the contents of the source to the Git manual.  It is
not all that unreasonable to expect

	git cat-file blob master:Documentation:git.txt

to be able to show the same thing as well.  You'd need to backtrack
the parsing (e.g. attempt to find "Documentation:git.txt" in
"master", fail to find any, then fall back to find "git.txt" in
"master:Documentation", find one, and be happy, or something like
that), and define how to resolve potential ambiguity (e.g. there may
indeed be "Documentation:git.txt" and "Documentation/git.txt" in the
tree-ish "master"), though.