Re: rerun

[Bruno Haible]

Hi Ralf,

> Wouldn't build-aux/rerun be a good candidate for a new gnulib module?

No, why would it? Packages don't ship 'rerun'. Only maintainers have it in
their PATH somewhere.

I haven't initiated moving 'git-merge-changelog' out of gnulib, where it
doesn't belong, just to repeat the same mistake with 'rerun'.

> Wrt. portability, this line:
> 
>     diff -u "$cachefile".old - | sed -e '1,2d' -e 
> '/^-/{s/^-/-'"$color_blue"'/;s/$/'"$color_off"'/}' -e 
> '/^+/{s/^+/+'"$color_red"'/;s/$/'"$color_off"'/}'
> 
> could profit from a quick test whether diff supports -u

The quality of the output depends on unified diff format. If the maintainer
does not have it installed, he needs to install it first.

> and the sed script something like
> 
>   sed -e '1,2d' \
>       -e '/^-/{' -e 's/^-/-'"$color_blue"'/' -e 's/$/'"$color_off"'/' -e '}' \
>       -e '/^+/{' -e 's/^+/+'"$color_red"'/' -e 's/$/'"$color_off"'/' -e '}'

No, it violates POSIX to pass several incomplete sed scripts as separate -e
arguments. You need to pass only complete sed scripts as -e arguments, if
necessary with newline. Quoting
<http://www.opengroup.org/onlinepubs/9699919799/utilities/sed.html>:
  "-e  script
               Add the editing commands specified by the script
               option-argument to the end of the script of editing commands.
               The script option-argument shall have the same properties as
               the script operand, described in the OPERANDS section."
Since you must not call
    sed '/^-/{'
you cannot use
    sed ... -e '/^-/{' ...

Yes I know GNU sed accepts this.

> then a --version option, and the script would be in pretty good shape
> already.  Maybe if the exit status could be nonzero if either the diff
> is nonempty or the $command failed, that would be neat.

Feel free to improve the script in any way you like!

Bruno