Re: [PATCH 2/2 v3] sha1_name: teach get_sha1_1 "-" shorthand for "@{-1}"

Junio C Hamano [off-list ref] writes:

Matthieu Moy [off-list ref] writes:

quoted

Siddharth Kannan [off-list ref] writes:

quoted

+	if (!strcmp(name, "-")) {
+		name = "@{-1}";
+		len = 5;
+	}

One drawback of this approach is that further error messages will be
given from the "@{-1}" string that the user never typed.

Right.

quoted

There are at least:

$ git grep -n -A1 'strcmp.*"-"' | grep -B 1 '@\{1\}'
builtin/checkout.c:975: if (!strcmp(arg, "-"))
builtin/checkout.c-976-         arg = "@{-1}";

I didn't check the surrounding context to be sure, but I think this
"- to @{-1}" conversion cannot be delegated down to revision parsing
that eventually wants to return a 40-hex as the result.  

We do want a branch _name_ sometimes when we say "@{-1}"; "checkout
master" (i.e. checkout by name) and "checkout master^0" (i.e. the
same commit object, but not by name) do different things.

FYI, the "@{-<number>} to branch name" translation happens in
interpret_branch_name().  I do not offhand recall if any callers
protect their calls to the function with conditionals that assume
the thing must begin with "@{" or cannot begin with "-" (the latter
of which is similar to the topic of patch 1/2 of this series), but I
suspect that teaching the function that "-" means the same as
"@{-1}" would bring us closer to where we want to go.