Merge branch 'jc/ll-merge-expose-path'

Traditionally, external low-level 3-way merge drivers are expected
to produce their results based solely on the contents of the three
variants given in temporary files named by %O, %A and %B on their
command line.  Additionally allow them to look at the final path
(given by %P).

* jc/ll-merge-expose-path:
  ll-merge: pass the original path to external drivers

Documentation/gitattributes.txt

@@ -774,7 +774,7 @@ To define a custom merge driver `filfre`, add a section to your
 ----------------------------------------------------------------
 [merge "filfre"]
 	name = feel-free merge driver
-	driver = filfre %O %A %B
+	driver = filfre %O %A %B %L %P
 	recursive = binary
 ----------------------------------------------------------------
 
@@ -800,6 +800,9 @@ merge between common ancestors, when there are more than one.
 When left unspecified, the driver itself is used for both
 internal merge and the final merge.
 
+The merge driver can learn the pathname in which the merged result
+will be stored via placeholder `%P`.
+
 
 `conflict-marker-size`
 ^^^^^^^^^^^^^^^^^^^^^^

ll-merge.c

@@ -9,6 +9,7 @@
 #include "xdiff-interface.h"
 #include "run-command.h"
 #include "ll-merge.h"
+#include "quote.h"
 
 struct ll_merge_driver;
 
@@ -166,17 +167,20 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 {
 	char temp[4][50];
 	struct strbuf cmd = STRBUF_INIT;
-	struct strbuf_expand_dict_entry dict[5];
+	struct strbuf_expand_dict_entry dict[6];
+	struct strbuf path_sq = STRBUF_INIT;
 	const char *args[] = { NULL, NULL };
 	int status, fd, i;
 	struct stat st;
 	assert(opts);
 
+	sq_quote_buf(&path_sq, path);
 	dict[0].placeholder = "O"; dict[0].value = temp[0];
 	dict[1].placeholder = "A"; dict[1].value = temp[1];
 	dict[2].placeholder = "B"; dict[2].value = temp[2];
 	dict[3].placeholder = "L"; dict[3].value = temp[3];
-	dict[4].placeholder = NULL; dict[4].value = NULL;
+	dict[4].placeholder = "P"; dict[4].value = path_sq.buf;
+	dict[5].placeholder = NULL; dict[5].value = NULL;
 
 	if (fn->cmdline == NULL)
 		die("custom merge driver %s lacks command line.", fn->name);
@@ -210,6 +214,7 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 	for (i = 0; i < 3; i++)
 		unlink_or_warn(temp[i]);
 	strbuf_release(&cmd);
+	strbuf_release(&path_sq);
 	return status;
 }
 
@@ -269,6 +274,7 @@ static int read_merge_config(const char *var, const char *value, void *cb)
 		 *    %A - temporary file name for our version.
 		 *    %B - temporary file name for the other branches' version.
 		 *    %L - conflict marker length
+		 *    %P - the original path (safely quoted for the shell)
 		 *
 		 * The external merge driver should write the results in the
 		 * file named by %A, and signal that it has done with zero exit

t/t6026-merge-attr.sh

@@ -85,11 +85,12 @@ test_expect_success 'retry the merge with longer context' '
 cat >./custom-merge <<\EOF
 #!/bin/sh
 
-orig="$1" ours="$2" theirs="$3" exit="$4"
+orig="$1" ours="$2" theirs="$3" exit="$4" path=$5
 (
 	echo "orig is $orig"
 	echo "ours is $ours"
 	echo "theirs is $theirs"
+	echo "path is $path"
 	echo "=== orig ==="
 	cat "$orig"
 	echo "=== ours ==="
@@ -110,7 +111,7 @@ test_expect_success 'custom merge backend' '
 
 	git reset --hard anchor &&
 	git config --replace-all \
-	merge.custom.driver "./custom-merge %O %A %B 0" &&
+	merge.custom.driver "./custom-merge %O %A %B 0 %P" &&
 	git config --replace-all \
 	merge.custom.name "custom merge driver for testing" &&
 
@@ -121,7 +122,7 @@ test_expect_success 'custom merge backend' '
 	o=$(git unpack-file master^:text) &&
 	a=$(git unpack-file side^:text) &&
 	b=$(git unpack-file master:text) &&
-	sh -c "./custom-merge $o $a $b 0" &&
+	sh -c "./custom-merge $o $a $b 0 'text'" &&
 	sed -e 1,3d $a >check-2 &&
 	cmp check-1 check-2 &&
 	rm -f $o $a $b
@@ -131,7 +132,7 @@ test_expect_success 'custom merge backend' '
 
 	git reset --hard anchor &&
 	git config --replace-all \
-	merge.custom.driver "./custom-merge %O %A %B 1" &&
+	merge.custom.driver "./custom-merge %O %A %B 1 %P" &&
 	git config --replace-all \
 	merge.custom.name "custom merge driver for testing" &&
 
@@ -148,9 +149,12 @@ test_expect_success 'custom merge backend' '
 	o=$(git unpack-file master^:text) &&
 	a=$(git unpack-file anchor:text) &&
 	b=$(git unpack-file master:text) &&
-	sh -c "./custom-merge $o $a $b 0" &&
+	sh -c "./custom-merge $o $a $b 0 'text'" &&
 	sed -e 1,3d $a >check-2 &&
 	cmp check-1 check-2 &&
+	sed -e 1,3d -e 4q $a >check-3 &&
+	echo "path is text" >expect &&
+	cmp expect check-3 &&
 	rm -f $o $a $b
 '