Merge branch 'jc/apply-binary-p0'

"git apply -p0" did not parse pathnames on "diff --git" line
correctly.  This caused patches that had pathnames in no other
places to be mistakenly rejected (most notably, binary patch that
does not rename nor change mode).  Textual patches, renames or
mode changes have preimage and postimage pathnames in different
places in a form that can be parsed unambiguously and did not suffer
from this problem.

* jc/apply-binary-p0:
  apply: compute patch->def_name correctly under -p0

1 files changed, 43 insertions, 25 deletions

diff --git a/builtin/apply.c b/builtin/apply.c
index 537d33b061..156b3ce3b7 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -1095,15 +1095,23 @@ static int gitdiff_unrecognized(const char *line, struct patch *patch)
 	return -1;
 }
 
-static const char *stop_at_slash(const char *line, int llen)
+/*
+ * Skip p_value leading components from "line"; as we do not accept
+ * absolute paths, return NULL in that case.
+ */
+static const char *skip_tree_prefix(const char *line, int llen)
 {
-	int nslash = p_value;
+	int nslash;
 	int i;
 
+	if (!p_value)
+		return (llen && line[0] == '/') ? NULL : line;
+
+	nslash = p_value;
 	for (i = 0; i < llen; i++) {
 		int ch = line[i];
 		if (ch == '/' && --nslash <= 0)
-			return &line[i];
+			return (i == 0) ? NULL : &line[i + 1];
 	}
 	return NULL;
 }
@@ -1133,12 +1141,11 @@ static char *git_header_name(const char *line, int llen)
 		if (unquote_c_style(&first, line, &second))
 			goto free_and_fail1;
 
-		/* advance to the first slash */
-		cp = stop_at_slash(first.buf, first.len);
-		/* we do not accept absolute paths */
-		if (!cp || cp == first.buf)
+		/* strip the a/b prefix including trailing slash */
+		cp = skip_tree_prefix(first.buf, first.len);
+		if (!cp)
 			goto free_and_fail1;
-		strbuf_remove(&first, 0, cp + 1 - first.buf);
+		strbuf_remove(&first, 0, cp - first.buf);
 
 		/*
 		 * second points at one past closing dq of name.
@@ -1152,22 +1159,21 @@ static char *git_header_name(const char *line, int llen)
 		if (*second == '"') {
 			if (unquote_c_style(&sp, second, NULL))
 				goto free_and_fail1;
-			cp = stop_at_slash(sp.buf, sp.len);
-			if (!cp || cp == sp.buf)
+			cp = skip_tree_prefix(sp.buf, sp.len);
+			if (!cp)
 				goto free_and_fail1;
 			/* They must match, otherwise ignore */
-			if (strcmp(cp + 1, first.buf))
+			if (strcmp(cp, first.buf))
 				goto free_and_fail1;
 			strbuf_release(&sp);
 			return strbuf_detach(&first, NULL);
 		}
 
 		/* unquoted second */
-		cp = stop_at_slash(second, line + llen - second);
-		if (!cp || cp == second)
+		cp = skip_tree_prefix(second, line + llen - second);
+		if (!cp)
 			goto free_and_fail1;
-		cp++;
-		if (line + llen - cp != first.len + 1 ||
+		if (line + llen - cp != first.len ||
 		    memcmp(first.buf, cp, first.len))
 			goto free_and_fail1;
 		return strbuf_detach(&first, NULL);
@@ -1179,10 +1185,9 @@ static char *git_header_name(const char *line, int llen)
 	}
 
 	/* unquoted first name */
-	name = stop_at_slash(line, llen);
-	if (!name || name == line)
+	name = skip_tree_prefix(line, llen);
+	if (!name)
 		return NULL;
-	name++;
 
 	/*
 	 * since the first name is unquoted, a dq if exists must be
@@ -1196,10 +1201,9 @@ static char *git_header_name(const char *line, int llen)
 			if (unquote_c_style(&sp, second, NULL))
 				goto free_and_fail2;
 
-			np = stop_at_slash(sp.buf, sp.len);
-			if (!np || np == sp.buf)
+			np = skip_tree_prefix(sp.buf, sp.len);
+			if (!np)
 				goto free_and_fail2;
-			np++;
 
 			len = sp.buf + sp.len - np;
 			if (len < second - name &&
@@ -1231,13 +1235,27 @@ static char *git_header_name(const char *line, int llen)
 		case '\n':
 			return NULL;
 		case '\t': case ' ':
-			second = stop_at_slash(name + len, line_len - len);
+			/*
+			 * Is this the separator between the preimage
+			 * and the postimage pathname?  Again, we are
+			 * only interested in the case where there is
+			 * no rename, as this is only to set def_name
+			 * and a rename patch has the names elsewhere
+			 * in an unambiguous form.
+			 */
+			if (!name[len + 1])
+				return NULL; /* no postimage name */
+			second = skip_tree_prefix(name + len + 1,
+						  line_len - (len + 1));
 			if (!second)
 				return NULL;
-			second++;
-			if (second[len] == '\n' && !strncmp(name, second, len)) {
+			/*
+			 * Does len bytes starting at "name" and "second"
+			 * (that are separated by one HT or SP we just
+			 * found) exactly match?
+			 */
+			if (second[len] == '\n' && !strncmp(name, second, len))
 				return xmemdupz(name, len);
-			}
 		}
 	}
 }