Update shell scripts to compute empty tree object ID

bk2204 · gitster · commit 03a7f388dafa · 2018-05-02T13:59:53.000+09:00
Several of our shell scripts hard-code the object ID of the empty tree.
To avoid any problems when changing hashes, compute this value on
startup of the script.  For performance, store the value in a variable
and reuse it throughout the life of the script.

Signed-off-by: brian m. carlson &lt;sandals@crustytoothpaste.net&gt;
Signed-off-by: Junio C Hamano &lt;gitster@pobox.com&gt;
diff --git a/git-filter-branch.sh b/git-filter-branch.sh
@@ -11,6 +11,8 @@
 # The following functions will also be available in the commit filter:
 
 functions=$(cat << \EOF
+EMPTY_TREE=$(git hash-object -t tree /dev/null)
+
 warn () {
 	echo "$*" >&2
 }
@@ -46,7 +48,7 @@ git_commit_non_empty_tree()
 {
 	if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then
 		map "$3"
-	elif test $# = 1 && test "$1" = 4b825dc642cb6eb9a060e54bf8d69288fbee4904; then
+	elif test $# = 1 && test "$1" = $EMPTY_TREE; then
 		:
 	else
 		git commit-tree "$@"
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
@@ -81,6 +81,8 @@ rewritten_pending="$state_dir"/rewritten-pending
 # and leaves CR at the end instead.
 cr=$(printf "\015")
 
+empty_tree=$(git hash-object -t tree /dev/null)
+
 strategy_args=${strategy:+--strategy=$strategy}
 test -n "$strategy_opts" &&
 eval '
@@ -238,7 +240,7 @@ is_empty_commit() {
 		die "$(eval_gettext "\$sha1: not a commit that can be picked")"
 	}
 	ptree=$(git rev-parse -q --verify "$1"^^{tree} 2>/dev/null) ||
-		ptree=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+		ptree=$empty_tree
 	test "$tree" = "$ptree"
 }
 
diff --git a/templates/hooks--pre-commit.sample b/templates/hooks--pre-commit.sample
@@ -12,7 +12,7 @@ then
 	against=HEAD
 else
 	# Initial commit: diff against an empty tree object
-	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
+	against=$(git hash-object -t tree /dev/null)
 fi
 
 # If you want to allow non-ASCII filenames set this variable to true.

Original file line number	Diff line number	Diff line change
`@@ -11,6 +11,8 @@`
`11`	`11`	`# The following functions will also be available in the commit filter:`
`12`	`12`
`13`	`13`	`functions=$(cat << \EOF`
	`14`	`+EMPTY_TREE=$(git hash-object -t tree /dev/null)`
	`15`	`+`
`14`	`16`	`warn () {`
`15`	`17`	`echo "$*" >&2`
`16`	`18`	`}`
`@@ -46,7 +48,7 @@ git_commit_non_empty_tree()`
`46`	`48`	`{`
`47`	`49`	`if test $# = 3 && test "$1" = $(git rev-parse "$3^{tree}"); then`
`48`	`50`	`map "$3"`
`49`		`- elif test $# = 1 && test "$1" = 4b825dc642cb6eb9a060e54bf8d69288fbee4904; then`
	`51`	`+ elif test $# = 1 && test "$1" = $EMPTY_TREE; then`
`50`	`52`	`:`
`51`	`53`	`else`
`52`	`54`	`git commit-tree "$@"`