Re: [PATCH] builtin-tag.c: Fix two memory leaks and minor notation changes.

> A repeated call to read_sha1_file was not freing memory
> when the buffer was allocated but returned size was zero.
> 
> Also, now the program does not allow many -F or -m options,
> which was a bug too because it was not freing the memory
> allocated for any previous -F or -m options.
> 
> Tests are provided for ensuring that only one option
> -F or -m is given. Also, another test is shipped here,
> to check that "git tag" fails when a non-existing file
> is passed to the -F option, something that git-tag.sh
> allowed creating the tag with an empty message.
> 
> Signed-off-by: Carlos Rica <jasampler@gmail.com>