Merge branch 'ae/better-template-failure-report' into maint

* ae/better-template-failure-report:
  Improve error messages when temporary file creation fails

Makefile

@@ -435,6 +435,7 @@ TEST_PROGRAMS_NEED_X += test-subprocess
 TEST_PROGRAMS_NEED_X += test-svn-fe
 TEST_PROGRAMS_NEED_X += test-treap
 TEST_PROGRAMS_NEED_X += test-index-version
+TEST_PROGRAMS_NEED_X += test-mktemp
 
 TEST_PROGRAMS = $(patsubst %,%$X,$(TEST_PROGRAMS_NEED_X))
 

t/t0070-fundamental.sh

@@ -12,4 +12,17 @@ test_expect_success 'character classes (isspace, isalpha etc.)' '
 	test-ctype
 '
 
+test_expect_success 'mktemp to nonexistent directory prints filename' '
+	test_must_fail test-mktemp doesnotexist/testXXXXXX 2>err &&
+	grep "doesnotexist/test" err
+'
+
+test_expect_success POSIXPERM 'mktemp to unwritable directory prints filename' '
+	mkdir cannotwrite &&
+	chmod -w cannotwrite &&
+	test_when_finished "chmod +w cannotwrite" &&
+	test_must_fail test-mktemp cannotwrite/testXXXXXX 2>err &&
+	grep "cannotwrite/test" err
+'
+
 test_done

test-mktemp.c

@@ -0,0 +1,14 @@
+/*
+ * test-mktemp.c: code to exercise the creation of temporary files
+ */
+#include "git-compat-util.h"
+
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		usage("Expected 1 parameter defining the temporary file template");
+
+	xmkstemp(xstrdup(argv[1]));
+
+	return 0;
+}

wrapper.c

@@ -198,10 +198,22 @@ FILE *xfdopen(int fd, const char *mode)
 int xmkstemp(char *template)
 {
 	int fd;
+	char origtemplate[PATH_MAX];
+	strlcpy(origtemplate, template, sizeof(origtemplate));
 
 	fd = mkstemp(template);
-	if (fd < 0)
-		die_errno("Unable to create temporary file");
+	if (fd < 0) {
+		int saved_errno = errno;
+		const char *nonrelative_template;
+
+		if (!template[0])
+			template = origtemplate;
+
+		nonrelative_template = make_nonrelative_path(template);
+		errno = saved_errno;
+		die_errno("Unable to create temporary file '%s'",
+			nonrelative_template);
+	}
 	return fd;
 }
 
@@ -321,10 +333,22 @@ int gitmkstemps(char *pattern, int suffix_len)
 int xmkstemp_mode(char *template, int mode)
 {
 	int fd;
+	char origtemplate[PATH_MAX];
+	strlcpy(origtemplate, template, sizeof(origtemplate));
 
 	fd = git_mkstemp_mode(template, mode);
-	if (fd < 0)
-		die_errno("Unable to create temporary file");
+	if (fd < 0) {
+		int saved_errno = errno;
+		const char *nonrelative_template;
+
+		if (!template[0])
+			template = origtemplate;
+
+		nonrelative_template = make_nonrelative_path(template);
+		errno = saved_errno;
+		die_errno("Unable to create temporary file '%s'",
+			nonrelative_template);
+	}
 	return fd;
 }