Re: [PATCH v1] builtin/checkout.c: replace bit-shift values for macros in call to check_stages

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

Edmundo Carmona Antoranz <eantoranz@gmail.com> writes:

> Currently a call to check_stages is using bit-shift values to
> define what will be used as the first argument. If the reader
> doesn't know what the values are from heart, they have to go dig
> in cache.h what each value is.
>
> This patch is replacing those values for the macros from cache.h so that it's
> clear at first sight what they are (CE_ENTRY_REMOVED, CE_ENTRY_ADDED)

The patch does not make sense.  The hardcoded numbers you touched
have nothing to do with these macros.

The first argument to check_stages() is a bitmask for the stage
numbers in the index (which can span from 1 to 3), where 1 means
"common ancestor", 2 means "ours" and 3 means "theirs".  The caller
gives a position 'pos' in the in-core index and asks the function
this question: "starting at position 'pos', there must be cache
entries with the same path as 'ce'---are these enries cover all the
stages specified by this mask?"  This particular caller wants to
make sure that there are both "ours" and "theirs" entries for the
path.

The thing is, CE_ENTRY_REMOVED may also happen to have the value of
4, but that has nothing to do with (1<<2) used in the argument of
this.  It was not chosen to be the value of 1 shifted by the stage
number for "ours".  Same thing for CE_ENTRY_ADDED and (1<<3).  Even
when these macros are renumbered, the argument to check_stages()
must stay the values they are written in the original code
(i.e. (1<<2)|(1<<3) == 12).

> Signed-off-by: Edmundo Carmona Antoranz <eantoranz@gmail.com>
> ---
>  builtin/checkout.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index ffa776c6e1..3a644b31f6 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -397,7 +397,7 @@ static int checkout_paths(const struct checkout_opts *opts,
>  			} else if (opts->writeout_stage) {
>  				errs |= check_stage(opts->writeout_stage, ce, pos, opts->overlay_mode);
>  			} else if (opts->merge) {
> -				errs |= check_stages((1<<2) | (1<<3), ce, pos);
> +				errs |= check_stages(CE_ENTRY_REMOVED | CE_ENTRY_ADDED, ce, pos);
>  			} else {
>  				errs = 1;
>  				error(_("path '%s' is unmerged"), ce->name);