[pacman-dev] [PATCH v2 2/2] Save backup files with extension .pacsave.n

[Pang Yan Han]

Teach pacman to save backup files with extension .pacsave.n, where n is a
positive integer. The current backup file shall be saved as <name>.pacsave,
while existing .pacsave.n files will be renamed to <name>.pacsave.n+1

Example:
1. You have subversion installed in your local repo. /etc/conf.d/svnserve
   is a file to be backed up. It contains local modifications

2. You remove subversion from your repo. /etc/conf.d/svnserve is backed up as
   /etc/conf.d/svnserve.pacsave

2. You install subversion again

3. You edit /etc/conf.d/svnserve

4. You remove subversion. The existing /etc/conf.d/svnserve.pacsave is renamed
   to /etc/conf.d/svnserve.pacsave.1 and /etc/conf.d/svnserve is backed up as
   /etc/conf.d/svnserve.pacsave

Signed-off-by: Pang Yan Han <pangyanhan at gmail.com>
---
 lib/libalpm/remove.c           |   75 ++++++++++++++++++++++++++++++++++++++++
 test/pacman/tests/remove012.py |   20 +++++++++++
 2 files changed, 95 insertions(+), 0 deletions(-)
 create mode 100644 test/pacman/tests/remove012.py

diff --git a/lib/libalpm/remove.c b/lib/libalpm/remove.c
index 83c437f..22c4e23 100644
--- a/lib/libalpm/remove.c
+++ b/lib/libalpm/remove.c
@@ -28,8 +28,11 @@
 #include <errno.h>
 #include <string.h>
 #include <limits.h>
+#include <dirent.h>
+#include <regex.h>
 #include <unistd.h>
 #include <sys/stat.h>
+#include <sys/types.h>
 
 /* libalpm */
 #include "remove.h"
@@ -218,6 +221,77 @@ static int can_remove_file(alpm_handle_t *handle, const alpm_file_t *file,
 	return 1;
 }
 
+static void shift_pacsave(alpm_handle_t *handle, const char *file)
+{
+	DIR *dir = NULL;
+	struct dirent *ent;
+	struct stat st;
+	regex_t reg;
+
+	const char *basename;
+	char *dirname;
+	char oldfile[PATH_MAX];
+	char newfile[PATH_MAX];
+	char regstr[PATH_MAX];
+
+	unsigned long log_max = 0;
+	size_t basename_len;
+
+	dirname = _alpm_mdirname(file);
+	if (!dirname) {
+		return;
+	}
+
+	basename = _alpm_mbasename(file);
+	basename_len = strlen(basename);
+
+	snprintf(regstr, PATH_MAX, "^%s\\.pacsave\\.([[:digit:]]+)$", basename);
+	if (regcomp(&reg, regstr, REG_EXTENDED | REG_NEWLINE) != 0) {
+		goto cleanup;
+	}
+
+	dir = opendir(dirname);
+	if (dir == NULL) {
+		_alpm_log(handle, ALPM_LOG_ERROR, _("could not open directory: %s: %s\n"),
+							dirname, strerror(errno));
+		goto cleanup;
+	}
+
+	while ((ent = readdir(dir)) != NULL) {
+		if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0) {
+			continue;
+		}
+
+		if (regexec(&reg, ent->d_name, 0, 0, 0) == 0) {
+			unsigned long cur_log;
+			cur_log = strtoul(ent->d_name + basename_len + strlen(".pacsave."), NULL, 10);
+			if (cur_log > log_max) {
+				log_max = cur_log;
+			}
+		}
+	}
+
+	/* Shift pacsaves */
+	unsigned long i;
+	for (i = log_max + 1; i > 1; i--) {
+		snprintf(oldfile, PATH_MAX, "%s.pacsave.%lu", file, i-1);
+		snprintf(newfile, PATH_MAX, "%s.pacsave.%lu", file, i);
+		rename(oldfile, newfile);
+	}
+
+	snprintf(oldfile, PATH_MAX, "%s.pacsave", file);
+	if (stat(oldfile, &st) == 0) {
+		snprintf(newfile, PATH_MAX, "%s.1", oldfile);
+		rename(oldfile, newfile);
+	}
+
+	regfree(&reg);
+
+cleanup:
+	free(dirname);
+	closedir(dir);
+}
+
 /* Helper function for iterating through a package's file and deleting them
  * Used by _alpm_remove_commit. */
 static void unlink_file(alpm_handle_t *handle, alpm_pkg_t *info,
@@ -298,6 +372,7 @@ static void unlink_file(alpm_handle_t *handle, alpm_pkg_t *info,
 				FREE(filehash);
 				if(cmp != 0) {
 					char newpath[PATH_MAX];
+					shift_pacsave(handle, file);
 					snprintf(newpath, PATH_MAX, "%s.pacsave", file);
 					rename(file, newpath);
 					_alpm_log(handle, ALPM_LOG_WARNING, _("%s saved as %s\n"), file, newpath);
diff --git a/test/pacman/tests/remove012.py b/test/pacman/tests/remove012.py
new file mode 100644
index 0000000..4274487
--- /dev/null
+++ b/test/pacman/tests/remove012.py
@@ -0,0 +1,20 @@
+self.description = "Remove a package with a modified file marked for backup and has existing pacsaves"
+
+self.filesystem = ["etc/dummy.conf.pacsave",
+                   "etc/dummy.conf.pacsave.1",
+                   "etc/dummy.conf.pacsave.2"]
+
+p1 = pmpkg("dummy")
+p1.files = ["etc/dummy.conf*"]
+p1.backup = ["etc/dummy.conf"]
+self.addpkg2db("local", p1)
+
+self.args = "-R %s" % p1.name
+
+self.addrule("PACMAN_RETCODE=0")
+self.addrule("!PKG_EXIST=dummy")
+self.addrule("!FILE_EXIST=etc/dummy.conf")
+self.addrule("FILE_PACSAVE=etc/dummy.conf")
+self.addrule("FILE_EXIST=etc/dummy.conf.pacsave.1")
+self.addrule("FILE_EXIST=etc/dummy.conf.pacsave.2")
+self.addrule("FILE_EXIST=etc/dummy.conf.pacsave.3")
-- 
1.7.6