The Git CodingGuidelines prefer the $(...) construct for command
substitution instead of using the backquotes `...`.

The backquoted form is the traditional method for command
substitution, and is supported by POSIX.  However, all but the
simplest uses become complicated quickly.  In particular, embedded
command substitutions and/or the use of double quotes require
careful escaping with the backslash character.

The patch was generated by:

for _f in $(find . -name "*.sh")
do
	perl -i -pe 'BEGIN{undef $/;} s/`(.+?)`/\$(\1)/smg'  "${_f}"
done

and then carefully proof-read.

Signed-off-by: Elia Pinto <gitter.spiros@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

For systems with a missing or broken perl, it is nicer to
explicitly say "we don't want perl" because:

  1. The Makefile knows not to bother with Perl-ish things
     like Git.pm.

  2. We can print a more user-friendly error message
     than "foo is not a git command" or whatever the broken
     perl might barf

  3. Test scripts that require perl can mark themselves and
     such and be skipped

This patch implements parts (1) and (2). The perl/
subdirectory is skipped entirely, gitweb is not built, and
any git commands which rely on perl will print a
human-readable message and exit with an error code.

This patch is based on one from Robin H. Johnson.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>