Re: [RFH/PATCH] blame: tighten command line parser

> The command line parser of "git blame" is prepared to take an
> ancient odd argument order "blame <path> <rev>" in addition to the
> usual "blame [<rev>] <path>".  It has at least two negative
> ramifications:
>
>  - In order to tell these two apart, it checks if the last command
>    line argument names a path in the working tree, using
>    file_exists().  However, "blame <rev> <path>" is a request to
>    explalin each and every line in the contents of <path> stored in

>    revision <rev> and does not need to have a working tree version
>    of the file.  A check with file_exists() is simply wrong.
>
>  - To coerce that mistaken file_exists() check to work, the code
>    calls setup_work_tree() before doing so, because the path it has
>    is relative to the top-level of the project tree.  However,
>    "blame <rev> <path>" MUST be usable even in a bare repository,
>    and there is no reason for letting setup_work_tree() to complain

>    and die with "This operation must be run in a work tree".
>
> To correct the former, switch to check if the last token is a
> revision (and if so, parse arguments using "blame <path> <rev>"
> rule).  Correct the latter by getting rid of setup_work_tree() and
> file_exists() check--the only case the call to this function matters
> is when we are running "blame <path>" (i.e. no starting revision and
> asking to blame the working tree file at <path>, digging through the
> HEAD revision), but there is a call in setup_scoreboard() just
> before it calls fake_working_tree_commit().
>
> Also attempt to give a bit more sensible error message when "blame
> XYZ" is given and XYZ cannot be a path.
>
>    side note: I am not happy with the "only one arg, which is a rev,
>    given in a bare repository" condition to give the new error
>    message, but this should be a good starting point.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>