From 09ecd36890b1b27214f5296134941177f07f9bfa Mon Sep 17 00:00:00 2001
From: tv <tv@shackspace.de>
Date: Sun, 11 Jan 2015 18:37:01 +0100
Subject: initial commit

---
 make-snapshot | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100755 make-snapshot

diff --git a/make-snapshot b/make-snapshot
new file mode 100755
index 0000000..d677c40
--- /dev/null
+++ b/make-snapshot
@@ -0,0 +1,75 @@
+#! /bin/sh
+#
+# make-snapshot {source-directory} {snapshot-directory}
+#
+set -euf
+
+source="$1"
+snapshot="$2"
+
+echo "source directory is $source"
+echo "snapshot directory is $snapshot"
+
+# TODO check whether $snapshot is a snapshot directory
+ls "$snapshot/by-date" >/dev/null
+
+# Set $link_dest to the latest snapshot, if there is one.
+# pre:
+#   $snapshot/by-date is a directory that contains only directories
+#   where names are produced by $(date +%Y-%d-%mT%H:%M:%S) or
+#   start with a . (and thus are not listed by ls).
+# post:
+#   $link_dest is set iff there is a latest snapshot
+#   $link_dest is set to the filename of the latest snapshot
+# 2012-11-08 tv TODO check pre-condition
+latest="$(ls -r "$snapshot/by-date" | grep ^[0-9] | head -n 1)"
+if test -n "$latest"; then
+  link_dest="$snapshot/by-date/$latest"
+  echo latest snapshot is $link_dest
+fi
+
+timestamp="$(date +%Y-%m-%dT%H:%M:%S)"
+complete="$snapshot/by-date/$timestamp"
+partial="$snapshot/by-date/.$timestamp.part"
+
+# TODO incooperate into ach's version
+if present_partials="$(ls -ar "$snapshot/by-date" | grep '^\..*\.part$')"; then
+case $(echo "$present_partials" | wc -l) in
+  (0) : ;; # nothing to do
+  (1)
+    echo "found partial snapshot: $present_partials"
+    printf "do you want to continue [y/N] "
+    read answer
+    case "$answer" in
+      (y|Y) partial="$snapshot/by-date/$present_partials";;
+      (*)
+        echo "abort"; exit 23
+        ;;
+    esac
+    ;;
+  (*)
+    echo "found too many partial snapshots:"
+    echo "$present_partials"
+    echo "abort"; exit 23
+    ;;
+esac
+fi
+
+# sync $source to $partial
+if test -d "${link_dest-}"; then
+  cp -al "$link_dest" "$partial"
+fi
+rsync -v \
+    -aAXF \
+    --delete \
+    "$source/" "$partial"
+sync
+
+mv "$partial" "$complete"
+sync
+
+# mark this snapshot as current
+rm -f "$snapshot/current"
+ln -snf "by-date/$timestamp" "$snapshot/current"
+
+echo "current snapshot is $(find "$snapshot/current" -exec readlink -f \{\} \;)"
-- 
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