remove #!interpreter line from shell libraries

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>

contrib/completion/git-completion.bash

@@ -1,5 +1,3 @@
-#!bash
-#
 # bash/zsh completion support for core Git.
 #
 # Copyright (C) 2006,2007 Shawn O. Pearce <spearce@spearce.org>

contrib/completion/git-completion.tcsh

@@ -1,5 +1,3 @@
-#!tcsh
-#
 # tcsh completion support for core Git.
 #
 # Copyright (C) 2012 Marc Khouzam <marc.khouzam@gmail.com>

git-mergetool--lib.sh

@@ -1,5 +1,4 @@
-#!/bin/sh
-# git-mergetool--lib is a library for common merge tool functions
+# git-mergetool--lib is a shell library for common merge tool functions
 
 : ${MERGE_TOOLS_DIR=$(git --exec-path)/mergetools}
 

git-parse-remote.sh

@@ -1,4 +1,6 @@
-#!/bin/sh
+# This is a shell library to calculate the remote repository and
+# upstream branch that should be pulled by "git pull" from the current
+# branch.
 
 # git-ls-remote could be called from outside a git managed repository;
 # this would fail in that case and would issue an error message.

git-rebase--am.sh

@@ -1,4 +1,5 @@
-#!/bin/sh
+# This shell script fragment is sourced by git-rebase to implement
+# its default, fast, patch-based, non-interactive mode.
 #
 # Copyright (c) 2010 Junio C Hamano.
 #

git-rebase--interactive.sh

@@ -1,11 +1,8 @@
-#!/bin/sh
+# This shell script fragment is sourced by git-rebase to implement
+# its interactive mode.  "git rebase --interactive" makes it easy
+# to fix up commits in the middle of a series and rearrange commits.
 #
 # Copyright (c) 2006 Johannes E. Schindelin
-
-# SHORT DESCRIPTION
-#
-# This script makes it easy to fix up commits in the middle of a series,
-# and rearrange commits.
 #
 # The original idea comes from Eric W. Biederman, in
 # http://article.gmane.org/gmane.comp.version-control.git/22407

git-rebase--merge.sh

@@ -1,4 +1,6 @@
-#!/bin/sh
+# This shell script fragment is sourced by git-rebase to implement
+# its merge-based non-interactive mode that copes well with renamed
+# files.
 #
 # Copyright (c) 2010 Junio C Hamano.
 #

git-sh-i18n.sh

@@ -1,9 +1,8 @@
-#!/bin/sh
+# This shell library is Git's interface to gettext.sh. See po/README
+# for usage instructions.
 #
 # Copyright (c) 2010 Ævar Arnfjörð Bjarmason
 #
-# This is Git's interface to gettext.sh. See po/README for usage
-# instructions.
 
 # Export the TEXTDOMAIN* data that we need for Git
 TEXTDOMAIN=git

git-sh-setup.sh

@@ -1,9 +1,6 @@
-#!/bin/sh
-#
-# This is included in commands that either have to be run from the toplevel
-# of the repository, or with GIT_DIR environment variable properly.
-# If the GIT_DIR does not look like the right correct git-repository,
-# it dies.
+# This shell scriplet is meant to be included by other shell scripts
+# to set up some variables pointing at the normal git directories and
+# a few helper shell functions.
 
 # Having this variable in your environment would break scripts because
 # you would cause "cd" to be taken to unexpected places.  If you

t/test-lib.sh

@@ -573,11 +573,9 @@ then
 
 	make_valgrind_symlink () {
 		# handle only executables, unless they are shell libraries that
-		# need to be in the exec-path.  We will just use "#!" as a
-		# guess for a shell-script, since we have no idea what the user
-		# may have configured as the shell path.
+		# need to be in the exec-path.
 		test -x "$1" ||
-		test "#!" = "$(head -c 2 <"$1")" ||
+		test "# " = "$(head -c 2 <"$1")" ||
 		return;
 
 		base=$(basename "$1")