cloudstorage: create consistent local directory names

With the new names for the cloud server we'd get different local cache
directory names depending on which server gets used. In order to avoid
that, normalize the name before generating the hash that determines the
local directory name.

Additionally, the old code had an extra '/' in the URL, due to the way
the URL was assembled. Again, to match the existing hash for people
upgrading from older Subsurface versions, add that to our normalized
name as well.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

core/git-access.c

@@ -130,11 +130,22 @@ static int push_transfer_progress_cb(unsigned int current, unsigned int total, s
 	return git_storage_update_progress(buf);
 }
 
-char *get_local_dir(const char *remote, const char *branch)
+char *get_local_dir(const char *remote_in, const char *branch)
 {
 	SHA_CTX ctx;
 	unsigned char hash[20];
 
+	// this optimization could in theory lead to odd things happening if the
+	// cloud backend servers ever get out of sync - but when a user switches
+	// between those servers (either because one is down, or because the algorithm
+	// which server to pick changed, or because the user is on a different continent),
+	// then the hash and therefore the local directory would change. To prevent that
+	// from happening, normalize the cloud string to always use the old default name.
+	// That's trivial with QString operations and painful to do right in plain C, so
+	// let's be lazy and call a C++ helper function
+	// just remember to free the string we get back
+	const char *remote = normalize_cloud_name(remote_in);
+
 	// That zero-byte update is so that we don't get hash
 	// collisions for "repo1 branch" vs "repo 1branch".
 	SHA1_Init(&ctx);
@@ -142,7 +153,7 @@ char *get_local_dir(const char *remote, const char *branch)
 	SHA1_Update(&ctx, "", 1);
 	SHA1_Update(&ctx, branch, strlen(branch));
 	SHA1_Final(hash, &ctx);
-
+	free((void *)remote);
 	return format_string("%s/cloudstorage/%02x%02x%02x%02x%02x%02x%02x%02x",
 			system_default_directory(),
 			hash[0], hash[1], hash[2], hash[3],

core/qthelper.cpp

@@ -22,6 +22,7 @@
 #include "trip.h"
 #include "imagedownloader.h"
 #include "xmlparams.h"
+#include "core/git-access.h" // for CLOUD_HOST definitions
 #include <QFile>
 #include <QRegExp>
 #include <QDir>
@@ -1455,6 +1456,15 @@ extern "C" char *cloud_url()
 	return copy_qstring(filename);
 }
 
+extern "C" const char *normalize_cloud_name(const char *remote_in)
+{
+	// replace ssrf-cloud-XX.subsurface... names with cloud.subsurface... names
+	// that trailing '/' is to match old code
+	QString ri(remote_in);
+	ri.replace(QRegularExpression(CLOUD_HOST_PATTERN), CLOUD_HOST_GENERIC "/");
+	return strdup(ri.toUtf8().constData());
+}
+
 extern "C" bool getProxyString(char **buffer)
 {
 	if (prefs.proxy_type == QNetworkProxy::HttpProxy) {

core/qthelper.h

@@ -147,6 +147,7 @@ void copy_image_and_overwrite(const char *cfileName, const char *path, const cha
 char *move_away(const char *path);
 const char *local_file_path(struct picture *picture);
 char *cloud_url();
+const char *normalize_cloud_name(const char *remote_in);
 char *hashfile_name_string();
 char *picturedir_string();
 const char *subsurface_user_agent();