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[PATCH v2 40/42] Update shell scripts to compute empty tree object ID

From
brian m. carlson <sandals@crustytoothpaste.net>
Date
May 2, 2018, 00:26 UTC
Message-ID
<20180502002610.915892-41-sandals@crustytoothpaste.net>
In-Reply-To
<20180502002610.915892-1-sandals@crustytoothpaste.net>

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 <sandals@crustytoothpaste.net>
---
 git-filter-branch.sh               | 4 +++-
 git-rebase--interactive.sh         | 4 +++-
 templates/hooks--pre-commit.sample | 2 +-
 3 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/git-filter-branch.sh b/git-filter-branch.sh
index 64f21547c1..ccceaf19a7 100755
--- 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
index 9947e6265f..e5ae58a07e 100644
--- 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
index 68d62d5446..6a75641638 100755
--- 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.
Previous: brian m. carlsonNext: brian m. carlson
Message 27 of 45 in “object_id part 13”
  1. 00/42 object_id part 13brian m. carlson, May 2, 2018
  2. 01/42 cache: add a function to read an object ID from a bufferbrian m. carlson, May 2, 2018
  3. 02/42 server-info: remove unused members from struct pack_infobrian m. carlson, May 2, 2018
  4. 06/42 sha1-file: convert freshen functions to object_idbrian m. carlson, May 2, 2018
  5. 07/42 packfile: convert find_pack_entry to object_idbrian m. carlson, May 2, 2018
  6. 11/42 tree-walk: avoid hard-coded 20 constantbrian m. carlson, May 2, 2018
  7. 05/42 packfile: convert has_sha1_pack to object_idbrian m. carlson, May 2, 2018
  8. 13/42 fsck: convert static functions to struct object_idbrian m. carlson, May 2, 2018
  9. 17/42 pack-redundant: convert linked lists to use struct object_idbrian m. carlson, May 2, 2018
  10. 15/42 split-index: convert struct split_index to object_idbrian m. carlson, May 2, 2018
  11. 14/42 submodule-config: convert structures to object_idbrian m. carlson, May 2, 2018
  12. 18/42 index-pack: abstract away hash function constantbrian m. carlson, May 2, 2018
  13. 12/42 tree-walk: convert get_tree_entry_follow_symlinks to object_idbrian m. carlson, May 2, 2018
  14. 10/42 pack-redundant: abstract away hash algorithmbrian m. carlson, May 2, 2018
  15. 09/42 pack-objects: abstract away hash algorithmbrian m. carlson, May 2, 2018
  16. 27/42 builtin/am: convert uses of EMPTY_TREE_SHA1_BIN to the_hash_algobrian m. carlson, May 2, 2018
  17. 28/42 builtin/merge: switch tree functions to use object_idbrian m. carlson, May 2, 2018
  18. 25/42 builtin/receive-pack: avoid hard-coded constants for push certsbrian m. carlson, May 2, 2018
  19. 35/42 sha1_file: convert cached object code to struct object_idbrian m. carlson, May 2, 2018
  20. 38/42 dir: use the_hash_algo for empty blob object IDbrian m. carlson, May 2, 2018
  21. 37/42 sequencer: use the_hash_algo for empty tree object IDbrian m. carlson, May 2, 2018
  22. 36/42 cache-tree: use is_empty_tree_oidbrian m. carlson, May 2, 2018
  23. 41/42 add--interactive: compute the empty tree valuebrian m. carlson, May 2, 2018
  24. 39/42 sha1_file: only expose empty object constants through git_hash_algobrian m. carlson, May 2, 2018
  25. 26/42 sha1-file: add functions for hex empty tree and blob OIDsbrian m. carlson, May 2, 2018
  26. 42/42 merge-one-file: compute empty blob object IDbrian m. carlson, May 2, 2018
  27. 40/42 Update shell scripts to compute empty tree object IDbrian m. carlson, May 2, 2018
  28. 34/42 builtin/reset: convert use of EMPTY_TREE_SHA1_BINbrian m. carlson, May 2, 2018
  29. 33/42 builtin/receive-pack: convert one use of EMPTY_TREE_SHA1_HEXbrian m. carlson, May 2, 2018
  30. 32/42 wt-status: convert two uses of EMPTY_TREE_SHA1_HEXbrian m. carlson, May 2, 2018
  31. 31/42 submodule: convert several uses of EMPTY_TREE_SHA1_HEXbrian m. carlson, May 2, 2018
  32. 30/42 sequencer: convert one use of EMPTY_TREE_SHA1_HEXbrian m. carlson, May 2, 2018
  33. 29/42 merge: convert empty tree constant to the_hash_algobrian m. carlson, May 2, 2018
  34. 23/42 upload-pack: replace use of several hard-coded constantsbrian m. carlson, May 2, 2018
  35. 22/42 revision: replace use of hard-coded constantsbrian m. carlson, May 2, 2018
  36. 24/42 diff: specify abbreviation size in terms of the_hash_algobrian m. carlson, May 2, 2018
  37. 16/42 Update struct index_state to use struct object_idbrian m. carlson, May 2, 2018
  38. 21/42 http: eliminate hard-coded constantsbrian m. carlson, May 2, 2018
  39. 20/42 dir: convert struct untracked_cache_dir to object_idbrian m. carlson, May 2, 2018
  40. 19/42 commit: convert uses of get_sha1_hex to get_oid_hexbrian m. carlson, May 2, 2018
  41. 08/42 packfile: abstract away hash constant valuesbrian m. carlson, May 2, 2018
  42. 04/42 packfile: remove unused member from struct pack_entrybrian m. carlson, May 2, 2018
  43. 03/42 Remove unused member in struct object_contextbrian m. carlson, May 2, 2018
  44. Duy NguyenMay 2, 2018
  45. brian m. carlsonMay 2, 2018

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