Save backup files with extension .pacsave.n

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@gmail.com>

Rebased from original email and adjusted for util-common usage.
Signed-off-by: Florian Pritz <bluewind@xinu.at>

Signed-off-by: Allan McRae <allan@archlinux.org>

1 files changed, 76 insertions, 0 deletions

diff --git a/lib/libalpm/remove.c b/lib/libalpm/remove.c
index b965391e..cdc572d9 100644
--- a/lib/libalpm/remove.c
+++ b/lib/libalpm/remove.c
@@ -26,8 +26,11 @@
 #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"
@@ -299,6 +302,78 @@ 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 = mdirname(file);
+	if(!dirname) {
+		return;
+	}
+
+	basename = 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);
+}
+
+
 /**
  * @brief Unlink a package file, backing it up if necessary.
  *
@@ -399,6 +474,7 @@ static int unlink_file(alpm_handle_t *handle, alpm_pkg_t *oldpkg,
 					char *newpath;
 					size_t len = strlen(file) + 8 + 1;
 					MALLOC(newpath, len, RET_ERR(handle, ALPM_ERR_MEMORY, -1));
+					shift_pacsave(handle, file);
 					snprintf(newpath, len, "%s.pacsave", file);
 					if(rename(file, newpath)) {
 						_alpm_log(handle, ALPM_LOG_ERROR, _("could not rename %s to %s (%s)\n"),