Enable "git rerere" by the config variable rerere.enabled

Earlier, "git rerere" was enabled by creating the directory
.git/rr-cache.  That is definitely not in line with most other
features, which are enabled by a config variable.

So, check the config variable "rerere.enabled". If it is set
to "false" explicitely, do not activate rerere, even if
.git/rr-cache exists. This should help when you want to disable
rerere temporarily.

If "rerere.enabled" is not set at all, fall back to detection
of the directory .git/rr-cache.

[jc: with minimum tweaks]

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -448,6 +448,11 @@ gc.rerereunresolved::
 	kept for this many days when `git rerere gc` is run.
 	The default is 15 days.  See gitlink:git-rerere[1].
 
+rerere.enabled::
+	Activate recording of resolved conflicts, so that identical
+	conflict hunks can be resolved automatically, should they
+	be encountered again.  See gitlink:git-rerere[1].
+
 gitcvs.enabled::
 	Whether the cvs server interface is enabled for this repository.
 	See gitlink:git-cvsserver[1].

Documentation/git-rerere.txt

@@ -23,7 +23,7 @@ initial manual merge, and later by noticing the same automerge
 results and applying the previously recorded hand resolution.
 
 [NOTE]
-You need to create `$GIT_DIR/rr-cache` directory to enable this
+You need to set the config variable rerere.enabled to enable this
 command.
 
 
@@ -171,7 +171,7 @@ records it if it is a new conflict, or reuses the earlier hand
 resolve when it is not.  `git-commit` also invokes `git-rerere`
 when recording a merge result.  What this means is that you do
 not have to do anything special yourself (Note: you still have
-to create `$GIT_DIR/rr-cache` directory to enable this command).
+to set the config variable rerere.enabled to enable this command).
 
 In our example, when you did the test merge, the manual
 resolution is recorded, and it will be reused when you do the

builtin-rerere.c

@@ -12,6 +12,9 @@ static const char git_rerere_usage[] =
 static int cutoff_noresolve = 15;
 static int cutoff_resolve = 60;
 
+/* if rerere_enabled == -1, fall back to detection of .git/rr-cache */
+static int rerere_enabled = -1;
+
 static char *merge_rr_path;
 
 static const char *rr_path(const char *name, const char *file)
@@ -387,21 +390,41 @@ static int git_rerere_config(const char *var, const char *value)
 		cutoff_resolve = git_config_int(var, value);
 	else if (!strcmp(var, "gc.rerereunresolved"))
 		cutoff_noresolve = git_config_int(var, value);
+	else if (!strcmp(var, "rerere.enabled"))
+		rerere_enabled = git_config_bool(var, value);
 	else
 		return git_default_config(var, value);
 	return 0;
 }
 
+static int is_rerere_enabled(void)
+{
+	struct stat st;
+	const char *rr_cache;
+	int rr_cache_exists;
+
+	if (!rerere_enabled)
+		return 0;
+
+	rr_cache = git_path("rr-cache");
+	rr_cache_exists = !stat(rr_cache, &st) && S_ISDIR(st.st_mode);
+	if (rerere_enabled < 0)
+		return rr_cache_exists;
+
+	if (!rr_cache_exists &&
+	    (mkdir(rr_cache, 0777) || adjust_shared_perm(rr_cache)))
+		die("Could not create directory %s", rr_cache);
+	return 1;
+}
+
 int cmd_rerere(int argc, const char **argv, const char *prefix)
 {
 	struct path_list merge_rr = { NULL, 0, 0, 1 };
 	int i, fd = -1;
-	struct stat st;
-
-	if (stat(git_path("rr-cache"), &st) || !S_ISDIR(st.st_mode))
-		return 0;
 
 	git_config(git_rerere_config);
+	if (!is_rerere_enabled())
+		return 0;
 
 	merge_rr_path = xstrdup(git_path("rr-cache/MERGE_RR"));
 	fd = hold_lock_file_for_update(&write_lock, merge_rr_path, 1);
@@ -411,6 +434,7 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
 		return do_plain_rerere(&merge_rr, fd);
 	else if (!strcmp(argv[1], "clear")) {
 		for (i = 0; i < merge_rr.nr; i++) {
+			struct stat st;
 			const char *name = (const char *)merge_rr.items[i].util;
 			if (!stat(git_path("rr-cache/%s", name), &st) &&
 					S_ISDIR(st.st_mode) &&

contrib/emacs/git.el

@@ -681,8 +681,7 @@ and returns the process output as a string."
                             (condition-case nil (delete-file ".git/MERGE_MSG") (error nil))
                             (with-current-buffer buffer (erase-buffer))
                             (git-set-files-state files 'uptodate)
-                            (when (file-directory-p ".git/rr-cache")
-                              (git-run-command nil nil "rerere"))
+                            (git-run-command nil nil "rerere")
                             (git-refresh-files)
                             (git-refresh-ewoc-hf git-status)
                             (message "Committed %s." commit)

git-am.sh

@@ -95,10 +95,7 @@ It does not apply to blobs recorded in its index."
     eval GITHEAD_$his_tree='"$SUBJECT"'
     export GITHEAD_$his_tree
     git-merge-recursive $orig_tree -- HEAD $his_tree || {
-	    if test -d "$GIT_DIR/rr-cache"
-	    then
 	    git rerere
-	    fi
 	    echo Failed to merge in the changes.
 	    exit 1
     }
@@ -252,10 +249,7 @@ last=`cat "$dotest/last"`
 this=`cat "$dotest/next"`
 if test "$skip" = t
 then
-	if test -d "$GIT_DIR/rr-cache"
-	then
 	git rerere clear
-	fi
 	this=`expr "$this" + 1`
 	resume=
 fi
@@ -420,10 +414,7 @@ do
 			stop_here_user_resolve $this
 		fi
 		apply_status=0
-		if test -d "$GIT_DIR/rr-cache"
-		then
 		git rerere
-		fi
 		;;
 	esac
 

git-commit.sh

@@ -610,10 +610,7 @@ rm -f "$GIT_DIR/COMMIT_MSG" "$GIT_DIR/COMMIT_EDITMSG" "$GIT_DIR/SQUASH_MSG"
 
 cd_to_toplevel
 
-if test -d "$GIT_DIR/rr-cache"
-then
-	git rerere
-fi
+git rerere
 
 if test "$ret" = 0
 then

git-merge.sh

@@ -496,9 +496,6 @@ Conflicts:
 		sed -e 's/^[^	]*	/	/' |
 		uniq
 	} >>"$GIT_DIR/MERGE_MSG"
-	if test -d "$GIT_DIR/rr-cache"
-	then
 	git rerere
-	fi
 	die "Automatic merge failed; fix conflicts and then commit the result."
 fi

git-rebase.sh

@@ -101,7 +101,7 @@ call_merge () {
 		return
 		;;
 	1)
-		test -d "$GIT_DIR/rr-cache" && git rerere
+		git rerere
 		die "$RESOLVEMSG"
 		;;
 	2)
@@ -159,11 +159,8 @@ do
 		;;
 	--skip)
 		if test -d "$dotest"
-		then
-			if test -d "$GIT_DIR/rr-cache"
 		then
 			git rerere clear
-			fi
 			prev_head="`cat $dotest/prev_head`"
 			end="`cat $dotest/end`"
 			msgnum="`cat $dotest/msgnum`"
@@ -181,10 +178,7 @@ do
 		exit
 		;;
 	--abort)
-		if test -d "$GIT_DIR/rr-cache"
-		then
 		git rerere clear
-		fi
 		if test -d "$dotest"
 		then
 			rm -r "$dotest"

t/t4200-rerere.sh

@@ -39,15 +39,32 @@ sed -e 's/To die, t/To die! T/' > a1
 echo "* END *" >>a1
 git commit -q -a -m second
 
-# activate rerere
-mkdir .git/rr-cache
+test_expect_success 'nothing recorded without rerere' '
+	(rm -rf .git/rr-cache; git config rerere.enabled false) &&
+	! git merge first &&
+	! test -d .git/rr-cache
+'
 
-test_expect_failure 'conflicting merge' 'git pull . first'
+# activate rerere, old style
+test_expect_success 'conflicting merge' '
+	git reset --hard &&
+	mkdir .git/rr-cache &&
+	git config --unset rerere.enabled &&
+	! git merge first
+'
 
 sha1=$(sed -e 's/	.*//' .git/rr-cache/MERGE_RR)
 rr=.git/rr-cache/$sha1
 test_expect_success 'recorded preimage' "grep ======= $rr/preimage"
 
+test_expect_success 'rerere.enabled works, too' '
+	rm -rf .git/rr-cache &&
+	git config rerere.enabled true &&
+	git reset --hard &&
+	! git merge first &&
+	grep ======= $rr/preimage
+'
+
 test_expect_success 'no postimage or thisimage yet' \
 	"test ! -f $rr/postimage -a ! -f $rr/thisimage"