Re: Shell script cleanups/style changes?

Junio C Hamano [off-list ref] writes:

David Kastrup [off-list ref] writes:

quoted

Hi, I wanted to ask what the general stance towards shell script
cleanups and simplifications would be.  For example, I find the
expr usage quite inscrutable in commit, and there is no necessity
of putting "shift" in every case branch instead of once behind it,
and a lot of conditionals and other manipulations can be made much
easier on the eye by using parameter expansion patterns that are,
as far as I can see, available with every reasonable Bourne Shell
and clones.

As to Bourne-ness of the shell script, please realize that your
maintainer is very old fashioned ;-), but is willing to be taught
new tricks within reason.

Most of the "new tricks" I try on bash, dash and ash.

We try to limit ourselves to -, =, ?, + (and their colon "if
empty" variants when it really make sense) in parameter
expansion of shell variables.  We also use % and # (and their
"match largest" variants).

You do?

Indeed:

-*- mode: grep; default-directory: "/home/tmp/git/" -*-
Grep started at Thu Aug  2 22:47:30

grep -nH -e '\${[a-zA-Z0-9_]*[#%]' *.sh
git-am.sh:146:	resolvemsg=${1#--resolvemsg=}; shift ;;
git-clone.sh:358:			destname="refs/$branch_top/${name#refs/heads/}" ;;
git-clone.sh:360:			destname="refs/$tag_top/${name#refs/tags/}" ;;
git-filter-branch.sh:361:		ref="${ref#refs/tags/}"
git-pull.sh:98:	curr_branch=${curr_branch#refs/heads/}
git-rebase.sh:93:	eval GITHEAD_$cmt='"${cmt_name##refs/heads/}~$(($end - $msgnum))"'
git-stash.sh:52:		branch=${branch#refs/heads/}

Grep finished (matches found) at Thu Aug  2 22:47:31

I am confused now: a different poster adamantly stated that /bin/sh on
Solaris did not support those constructs, and that every functionality
of git was working fine for him.

Non POSIX substitions such as ${parameter/pattern/string} and
${parameter:offset} are not to be used.  We do not want to
depend on bash.

Sure.  What about the git-rebase line using $(($end - $msgnum)) ?
That's even more risque than ##.

After 1.5.3 git-commit.sh will hopefully become built-in, so I would
rather not touch the script.

Too bad: this should mean that $EDITOR can get called from C...  I've
been glad to see that so far this could be avoided.

Certainly, the kind of change that is "intended to be style-only but
somebody needs to make sure it does not introduce regression to
everybody's shell" is very unwelcome at this point.

Understood.  But using ${...#...} and ${...:+...} does not exactly
seem to be news in the git code base.  Even though we have the claim
that Solaris' sh won't deal with the former.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum