Re: [PATCH] rev-parse: clarify documentation for the --verify option

Michael Haggerty [off-list ref] writes:

...  Though honestly, I don't see the point of using
--default as opposed to

    $ git rev-parse --verify ${REV:-master}^{commit}

I would agree ${VAR:-default} is sufficient in that particular case.

The --default is more about the use of the pluming command not with
--verify but as its original use of an "argument sifter" when
composing "git rev-list" piped into "git diff-tree --stdin", i.e.

	git rev-list $(git rev-parse --default HEAD --revs-only "$@") |
        git diff-tree --stdin $(git rev-parse --no-revs "$@")

which was the original way to write commands in the "git log" family
using the plumbing command as a scripted Porcelain.

 --verify::
+	If the parameter can be used as a single object name, output
+	that name; otherwise, emit an error message and exit with a
+	non-zero status.  Please note that the existence and validity
+	of the named object itself are not checked.

Perhaps s/used as a single object name/turned into a raw 20-byte SHA-1/;

Because the primary use case of this option is to implement end-user
input validation, I think it would be helpful to clarify use of the
peeler here.  Perhaps

    --verify::
            Make sure the single given parameter can be turned into a
            raw 20-byte SHA-1, something that can be used to access the
            object database, and emit the SHA-1 in 40-hex format (unless
            --symbolic and other formatting option is given); otherwise,
            error out.
    +
    If you want to make sure that the output from this actually
    names an object in your object database and/or can be used
    as a specific type of object you require, it is a good idea
    to add "^{type}" peeling operator to the parmeter.  For
    example, `git rev-parse "$VAR^{commit}"` will make sure $VAR
    names an existing object that is a commit-ish (i.e. a
    commit, or an annotated tag that points at a commit).  To
    make sure that $VAR names an existing object of any type,
    you can say `git rev-parse "$VAR^{object}"`.

or something.