Always create snapshots

Prior to this commit, zap would only create new snapshots for filesystem
that had changed since the last snapshot.  If there were no changes,
then the name of the most recent snapshot would be updated with the
current date.  There were problems with this logic, so just
unconditionally create the snapshot.

README.org

@@ -7,7 +7,7 @@
 *** Key features
     - no configuration files
     - uses "namespaces" to avoid collisions with other snapshots
-    - creates and destroys snapshots only when it makes sense [2][3]
+    - creates and destroys snapshots only when it makes sense [2]
     - written in POSIX sh
 
 ** Synopsis
@@ -80,8 +80,4 @@ SHELL=/bin/sh
 [1] zap was influenced by zfSnap, which is under a BEER-WARE license.
 We owe the author a beer.
 
-[2] New snapshots are only created when a filesystem has changed since the last
-snapshot.  If the filesystem has not changed, then the timestamp of the newest
-snapshot is updated.
-
-[3] If the pool is in a DEGRADED state, zap will not destroy snapshots.
+[2] If the pool is in a DEGRADED state, zap will not destroy snapshots.

zap

@@ -41,11 +41,7 @@
 # [1] zap was influenced by zfSnap, which is under a BEER-WARE license.  We owe
 # the authors a beer.
 #
-# [2] New snapshots are only created when a filesystem has changed since the
-# last snapshot.  If the filesystem has not changed, then the timestamp of the
-# newest snapshot is updated.
-#
-# [3] If the pool is in a DEGRADED state, zap will not destroy snapshots.
+# [2] If the pool is in a DEGRADED state, zap will not destroy snapshots.
 #
 
 fatal () {
@@ -54,7 +50,7 @@ fatal () {
 }
 
 help () {
-    readonly version=0.3.0
+    readonly version=0.4.0
 
     cat <<EOF
 NAME
@@ -145,18 +141,7 @@ create () {
                 grep -q "FAULTED\|OFFLINE\|REMOVED\|UNAVAIL"; then
             warn "zap skipped creating a snapshot for $i because of pool state!"
         else
-            r=$(zfs list -rHo name -t snap -S name "$i" | grep "${i}${zptn}" | \
-                    grep -e "--${ttl}" -m1)
-            if [ ! -z "$r" ]; then
-                s=$(zfs get -H -o value written "$r")
-                if [ "${s}" != "0" ]; then
-                    zfs snapshot "${i}@ZAP_${date}--${ttl}"
-                else
-                    zfs rename "${r}" "${i}@ZAP_${date}--${ttl}"
-                fi
-            else
-                zfs snapshot "${i}@ZAP_${date}--${ttl}"
-            fi
+            zfs snapshot "${i}@ZAP_${date}--${ttl}"
         fi
     done
 }