git_config_string janitorial conversions.

index e3ad38b..745c11e 100644
@@ -45,7 +45,8 @@ static enum {
 	COMMIT_PARTIAL,
 } commit_style;
 
-static char *logfile, *force_author, *template_file;
+static char *logfile, *force_author;
+static const char *template_file;
 static char *edit_message, *use_message;
 static char *author_name, *author_email, *author_date;
 static int all, edit_flag, also, interactive, only, amend, signoff;

@@ -877,12 +878,8 @@ static void print_summary(const char *prefix, const unsigned char *sha1)
 
 int git_commit_config(const char *k, const char *v, void *cb)
 {
-	if (!strcmp(k, "commit.template")) {
-		if (!v)
-			return config_error_nonbool(v);
-		template_file = xstrdup(v);
-		return 0;
-	}
+	if (!strcmp(k, "commit.template"))
+		return git_config_string(&template_file, k, v);
 
 	return git_status_config(k, v, cb);
 }

index 9979e37..430d876 100644
@@ -234,12 +234,8 @@ static int git_log_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "format.pretty"))
 		return git_config_string(&fmt_pretty, var, value);
-	if (!strcmp(var, "format.subjectprefix")) {
-		if (!value)
-			config_error_nonbool(var);
-		fmt_patch_subject_prefix = xstrdup(value);
-		return 0;
-	}
+	if (!strcmp(var, "format.subjectprefix"))
+		return git_config_string(&fmt_patch_subject_prefix, var, value);
 	if (!strcmp(var, "log.date"))
 		return git_config_string(&default_date_mode, var, value);
 	if (!strcmp(var, "log.showroot")) {

@@ -489,12 +485,8 @@ static int git_format_config(const char *var, const char *value, void *cb)
 		add_header(value);
 		return 0;
 	}
-	if (!strcmp(var, "format.suffix")) {
-		if (!value)
-			return config_error_nonbool(var);
-		fmt_patch_suffix = xstrdup(value);
-		return 0;
-	}
+	if (!strcmp(var, "format.suffix"))
+		return git_config_string(&fmt_patch_suffix, var, value);
 	if (!strcmp(var, "format.cc")) {
 		if (!value)
 			return config_error_nonbool(var);

index 1c66844..352b69d 100644
@@ -319,8 +319,8 @@ static int apply_filter(const char *path, const char *src, size_t len,
 static struct convert_driver {
 	const char *name;
 	struct convert_driver *next;
-	char *smudge;
-	char *clean;
+	const char *smudge;
+	const char *clean;
 } *user_convert, **user_convert_tail;
 
 static int read_convert_config(const char *var, const char *value, void *cb)

@@ -358,19 +358,12 @@ static int read_convert_config(const char *var, const char *value, void *cb)
 	 * The command-line will not be interpolated in any way.
 	 */
 
-	if (!strcmp("smudge", ep)) {
-		if (!value)
-			return config_error_nonbool(var);
-		drv->smudge = strdup(value);
-		return 0;
-	}
+	if (!strcmp("smudge", ep))
+		return git_config_string(&drv->smudge, var, value);
+
+	if (!strcmp("clean", ep))
+		return git_config_string(&drv->clean, var, value);
 
-	if (!strcmp("clean", ep)) {
-		if (!value)
-			return config_error_nonbool(var);
-		drv->clean = strdup(value);
-		return 0;
-	}
 	return 0;
 }
 

@@ -576,7 +569,7 @@ int convert_to_git(const char *path, const char *src, size_t len,
 	struct git_attr_check check[3];
 	int crlf = CRLF_GUESS;
 	int ident = 0, ret = 0;
-	char *filter = NULL;
+	const char *filter = NULL;
 
 	setup_convert_check(check);
 	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {

@@ -606,7 +599,7 @@ int convert_to_working_tree(const char *path, const char *src, size_t len, struc
 	struct git_attr_check check[3];
 	int crlf = CRLF_GUESS;
 	int ident = 0, ret = 0;
-	char *filter = NULL;
+	const char *filter = NULL;
 
 	setup_convert_check(check);
 	if (!git_checkattr(path, ARRAY_SIZE(check), check)) {

index 803fbba..6a39b39 100644
@@ -153,12 +153,8 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		diff_auto_refresh_index = git_config_bool(var, value);
 		return 0;
 	}
-	if (!strcmp(var, "diff.external")) {
-		if (!value)
-			return config_error_nonbool(var);
-		external_diff_cmd_cfg = xstrdup(value);
-		return 0;
-	}
+	if (!strcmp(var, "diff.external"))
+		return git_config_string(&external_diff_cmd_cfg, var, value);
 	if (!prefixcmp(var, "diff.")) {
 		const char *ep = strrchr(var, '.');
 

index 105dc93..c22adcc 100644
@@ -13,14 +13,14 @@ static CURL *curl_default;
 char curl_errorstr[CURL_ERROR_SIZE];
 
 static int curl_ssl_verify = -1;
-static char *ssl_cert = NULL;
+static const char *ssl_cert = NULL;
 #if LIBCURL_VERSION_NUM >= 0x070902
-static char *ssl_key = NULL;
+static const char *ssl_key = NULL;
 #endif
 #if LIBCURL_VERSION_NUM >= 0x070908
-static char *ssl_capath = NULL;
+static const char *ssl_capath = NULL;
 #endif
-static char *ssl_cainfo = NULL;
+static const char *ssl_cainfo = NULL;
 static long curl_low_speed_limit = -1;
 static long curl_low_speed_time = -1;
 static int curl_ftp_no_epsv = 0;

@@ -100,39 +100,27 @@ static int http_options(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp("http.sslcert", var)) {
-		if (ssl_cert == NULL) {
-			if (!value)
-				return config_error_nonbool(var);
-			ssl_cert = xstrdup(value);
-		}
+		if (ssl_cert == NULL)
+			return git_config_string(&ssl_cert, var, value);
 		return 0;
 	}
 #if LIBCURL_VERSION_NUM >= 0x070902
 	if (!strcmp("http.sslkey", var)) {
-		if (ssl_key == NULL) {
-			if (!value)
-				return config_error_nonbool(var);
-			ssl_key = xstrdup(value);
-		}
+		if (ssl_key == NULL)
+			return git_config_string(&ssl_key, var, value);
 		return 0;
 	}
 #endif
 #if LIBCURL_VERSION_NUM >= 0x070908
 	if (!strcmp("http.sslcapath", var)) {
-		if (ssl_capath == NULL) {
-			if (!value)
-				return config_error_nonbool(var);
-			ssl_capath = xstrdup(value);
-		}
+		if (ssl_capath == NULL)
+			return git_config_string(&ssl_capath, var, value);
 		return 0;
 	}
 #endif
 	if (!strcmp("http.sslcainfo", var)) {
-		if (ssl_cainfo == NULL) {
-			if (!value)
-				return config_error_nonbool(var);
-			ssl_cainfo = xstrdup(value);
-		}
+		if (ssl_cainfo == NULL)
+			return git_config_string(&ssl_cainfo, var, value);
 		return 0;
 	}