[PATCH v2 2/2] setup: Don't dereference in-tree symlinks for absolute paths

[Martin Erik Werner <martinerikwerner@gmail.com>]

The prefix_path_gently() function currently applies real_path to
everything if given an absolute path, dereferencing symlinks both
outside and inside the work tree. In order to manipulate symliks in the
work tree using absolute paths, symlinks should only be dereferenced
outside the work tree.

Modify prefix_path_gently() to first normalize the path in order to
make sure path levels are separated by '/', then use this separator to
check the real path of each level of the path until it has found the
length that corresponds to the work tree.

For absolute paths, the function did not, nor does now do, any actual
prefixing, hence we simply remove the path corresponding to the work
tree and return the remaining in-tree part of the path.

Fixes t0060-82.

Signed-off-by: Martin Erik Werner <martinerikwerner@gmail.com>
---
 setup.c               | 64 +++++++++++++++++++++++++++++++++++----------------
 t/t0060-path-utils.sh |  2 +-
 2 files changed, 45 insertions(+), 21 deletions(-)

diff --git a/setup.c b/setup.c
index 5432a31..0789a96 100644
--- a/setup.c
+++ b/setup.c
@@ -22,11 +22,51 @@ char *prefix_path_gently(const char *prefix, int len,
 	const char *orig = path;
 	char *sanitized;
 	if (is_absolute_path(orig)) {
-		const char *temp = real_path(path);
-		sanitized = xmalloc(len + strlen(temp) + 1);
-		strcpy(sanitized, temp);
+		int i, match;
+		size_t wtpartlen;
+		char *npath, *wtpart;
+		struct string_list list = STRING_LIST_INIT_DUP;
+		const char *work_tree = get_git_work_tree();
+		if (!work_tree)
+			return NULL;
+		npath = xmalloc(strlen(path) + 1);
 		if (remaining_prefix)
 			*remaining_prefix = 0;
+		if (normalize_path_copy_len(npath, path, remaining_prefix)) {
+			free(npath);
+			return NULL;
+		}
+
+		string_list_split(&list, npath, '/', -1);
+		wtpart = xmalloc(strlen(npath) + 1);
+		i = 0;
+		match = 0;
+		strcpy(wtpart, list.items[i++].string);
+		strcat(wtpart, "/");
+		if (strcmp(real_path(wtpart), work_tree) == 0) {
+			match = 1;
+		} else {
+			while (i < list.nr) {
+				strcat(wtpart, list.items[i++].string);
+				if (strcmp(real_path(wtpart), work_tree) == 0) {
+					match = 1;
+					break;
+				}
+				strcat(wtpart, "/");
+			}
+		}
+		string_list_clear(&list, 0);
+		if (!match) {
+			free(npath);
+			free(wtpart);
+			return NULL;
+		}
+
+		wtpartlen = strlen(wtpart);
+		sanitized = xmalloc(strlen(npath) - wtpartlen);
+		strcpy(sanitized, npath + wtpartlen + 1);
+		free(npath);
+		free(wtpart);
 	} else {
 		sanitized = xmalloc(len + strlen(path) + 1);
 		if (len)
@@ -34,26 +74,10 @@ char *prefix_path_gently(const char *prefix, int len,
 		strcpy(sanitized + len, path);
 		if (remaining_prefix)
 			*remaining_prefix = len;
-	}
-	if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix))
-		goto error_out;
-	if (is_absolute_path(orig)) {
-		size_t root_len, len, total;
-		const char *work_tree = get_git_work_tree();
-		if (!work_tree)
-			goto error_out;
-		len = strlen(work_tree);
-		root_len = offset_1st_component(work_tree);
-		total = strlen(sanitized) + 1;
-		if (strncmp(sanitized, work_tree, len) ||
-		    (len > root_len && sanitized[len] != '\0' && sanitized[len] != '/')) {
-		error_out:
+		if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix)) {
 			free(sanitized);
 			return NULL;
 		}
-		if (sanitized[len] == '/')
-			len++;
-		memmove(sanitized, sanitized + len, total - len);
 	}
 	return sanitized;
 }
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 3a0677a..03a12ac 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -190,7 +190,7 @@ test_expect_success SYMLINKS 'real path works on symlinks' '
 	test "$sym" = "$(test-path-utils real_path "$dir2/syml")"
 '
 
-test_expect_failure SYMLINKS 'prefix_path works with work tree symlinks' '
+test_expect_success SYMLINKS 'prefix_path works with work tree symlinks' '
 
 	ln -s target symlink &&
 	test "$(test-path-utils prefix_path prefix "$(pwd)/symlink")" = "symlink"
-- 
1.8.5.2