Make `update@` as a reserved prefix for snapshot name

doc/66-snapshot.md

@@ -76,6 +76,8 @@ This subcommand make a snapshot called *named* containing a verbatim copy of the
 
 `%%livedir%%`, `%%system_log%%` and `$HOME/%%user_log%%` for regular users are not taken into account.
 
+The prefix `update@` is reserved for snapshot names used in automatic upgrade processes. Please consider to choose a different prefix for your personal. snapshot names.
+
 #### Options
 
 - **-h**: prints this help.

src/lib66/exec/ssexec_snapshot_create.c

@@ -152,6 +152,9 @@ int ssexec_snapshot_create(int argc, char const *const *argv, ssexec_t *info)
 
     snapname = *argv ;
 
+    if (!str_start_with(snapname, "update@"))
+        log_die(LOG_EXIT_USER, "update@ is a reserved prefix for snapshot names -- please select a different one") ;
+
     auto_strings(snapdir.s, info->base.s, SS_SNAPSHOT + 1) ;
 
     len = info->base.len + (SS_SNAPSHOT_LEN - 1) ;

src/lib66/exec/ssexec_snapshot_restore.c

@@ -20,6 +20,7 @@
 #include <oblibs/string.h>
 #include <oblibs/stack.h>
 #include <oblibs/sastr.h>
+#include <oblibs/directory.h>
 
 #include <skalibs/sgetopt.h>
 #include <skalibs/djbunix.h>
@@ -102,6 +103,17 @@ int ssexec_snapshot_restore(int argc, char const *const *argv, ssexec_t *info)
             log_dieusys(LOG_EXIT_SYS, "copy: ", src.s," to: ", dst.s) ;
     }
 
+    auto_strings(src.s, snapdir.s, "/", SS_SYSTEM, "/.version") ;
+
+    /** remove .version file if it doesn't exist at snapshot dir.
+     * Typically version under 0.8.0.0 do not have this file.*/
+    if (access(src.s, F_OK) < 0) {
+        auto_strings(src.s, info->base.s, SS_SYSTEM, "/.version") ;
+
+        if (!dir_rm_rf(src.s))
+            log_warnusys("remove file: ", src.s) ;
+    }
+
     log_info("Successfully restored snapshot: ", snapname) ;
 
     return 0 ;

src/lib66/migrate/migrate_0721.c

@@ -610,12 +610,12 @@ static void migrate_create_snap_0721(ssexec_t *info)
     info->usage = usage_snapshot_create ;
 
     newargv[m++] = "snapshot" ;
-    newargv[m++] = "0.7.2.1" ;
+    newargv[m++] = "update@0.7.2.1" ;
     newargv[m] = 0 ;
 
     PROG = "snapshot" ;
     if (ssexec_snapshot_create(m, newargv, info))
-        log_dieu(LOG_EXIT_SYS, "create snapshot: ", "0.7.2.1") ;
+        log_dieu(LOG_EXIT_SYS, "create snapshot update@0.7.2.1") ;
     PROG = prog ;
 
     info->help = help ;