Re: [PATCH] Documentation/githooks: Explain pre-rebase parameters

"W. Trevor King" [off-list ref] writes:

I'm not 100% convinced about this, because the git-rebase.sh uses:

  "$GIT_DIR/hooks/pre-rebase" ${1+"$@"}

I haven't been able to find documentation for the ${1+"$@"} syntax.
Is it in POSIX?  It's not in the Bash manual:

[...]

In my local tests, it seems equivalent to "$@".

It's definitely in the bash manual and POSIX[1]: it's a special case of
the ${parameter+word} expansion.

   ${parameter:+word}
      Use Alternate Value.  If parameter is null or unset, nothing is
      substituted, otherwise the expansion of word is substituted.

plus

   ... bash tests for a parameter that is unset or null.  Omitting the
   colon results in a test only for a parameter that is unset.

IIRC this particular usage was designed to suppress warnings about unset
variables.


Footnotes: 
[1]  http://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html

-- 
Thomas Rast
trast@{inf,student}.ethz.ch