In a shell snippet meant to be sourced by other shell scripts, an
opening #! line does more harm than good.
The harm:
- When the shell library is sourced, the interpreter and options from
the #! line are not used. Specifying a particular shell can
confuse the reader into thinking it is safe for the shell library
to rely on idiosyncrasies of that shell.
- Using #! instead of a plain comment drops a helpful visual clue
that this is a shell library and not a self-contained script.
- Tools such as lintian can use a #! line to tell when an
installation script has failed by forgetting to set a script
executable. This check does not work if shell libraries also start
with a #! line.
The good:
- Text editors notice the #! line and use it for syntax highlighting
if you try to edit the installed scripts (without ".sh" suffix) in
place.
The use of the #! for file type detection is not needed because Git's
shell libraries are meant to be edited in source form (with ".sh"
suffix). Replace the opening #! lines with comments.
This involves tweaking the test harness's valgrind support to find
shell libraries by looking for "# " in the first line instead of "#!"
(see v1.7.6-rc3~7, 2011-06-17).
Suggested by Russ Allbery through lintian. Thanks to Jeff King and
Clemens Buchacher for further analysis.
Tested by searching for non-executable scripts with #! line:
find . -name .git -prune -o -type f -not -executable |
while read file
do
read line <"$file"
case $line in
'#!'*)
echo "$file"
;;
esac
done
The only remaining scripts found are templates for shell scripts
(unimplemented.sh, wrap-for-bin.sh) and sample input used in tests
(t/t4034/perl/{pre,post}).
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>