3 files changed, 114 insertions, 0 deletions
diff --git a/pkgs/btclone/btclone.nix b/pkgs/btclone/btclone.nix
new file mode 100755
index 0000000..dce0cde
--- /dev/null
+++ b/pkgs/btclone/btclone.nix
@@ -0,0 +1,107 @@
+''
+  usage() { echo "Usage: $0 <subvolume> <target> [<up-to>]" >&2; exit 1; }
+  
+  [[ $# -ge 2 && $# -le 3 && ( $# -ne 3 || $(("$3" + 0)) = "$3" ) ]] || usage
+  [[ $UID -eq 0 ]] || { echo "$0: requires root privileges" >&2; exit 1; }
+  
+  SOURCE="$1"
+  TARGET="$2"
+  [ $# -ge 3 ] && UP_TO="$3" || UP_TO=
+  
+  get_snapshots() {
+      FILTER="\$1 > 0"
+      [[ -n "$UP_TO" ]] && FILTER="\$1 > 0 && \$1 <= $UP_TO"
+
+      find "$1" -follow -maxdepth 1 -printf '%f\n' \
+          | sed 's@/$@@g' | awk "$FILTER { print }" | sort -n
+  }
+  
+  clone() {
+      if [[ -n "$2" ]]; then
+          echo "Cloning $1 (incremental from $2)..." >&2
+          PARENT_ARG="-p$SOURCE/$2/snapshot"
+      else
+          echo "Cloning $1 (non-incremental)..." >&2
+      fi
+  
+      FROM="$SOURCE/$1"
+      INTO="$TARGET/$1"
+  
+      [[ -d "$INTO" ]] || mkdir "$INTO"
+      btrfs send "$PARENT_ARG" "$FROM/snapshot" | pv | btrfs receive "$INTO"
+      cp -a "$FROM/info.xml" "$INTO/"
+  }
+  
+  cleanup() {
+      echo "Removing $1..." >&2
+  
+      AT="$TARGET/$1"
+      [[ -d "$AT/snapshot" ]] && btrfs subvolume delete "$AT/snapshot"
+      rm -f "$AT/info.xml"
+      rmdir "$AT"
+  }
+  
+  while true; do
+      ls -- "$SOURCE/" "$TARGET/" >/dev/null
+      mapfile -t SNAPSHOTS < <(get_snapshots "$SOURCE")
+      [[ ''${#SNAPSHOTS} -eq 0 ]] && { echo "$0: nothing to do" >&2; exit; }
+      mapfile -t EXISTENT < <(get_snapshots "$TARGET")
+  
+      RESET=0
+      PARENT=
+      ALL_ARE_BAD=0
+      for SNAPSHOT in "''${SNAPSHOTS[@]}"; do
+          if [[ ! -e "$SOURCE/$SNAPSHOT" ]]; then
+              echo "Notice: resetting listings due to time lapse" >&2
+  
+              RESET=1
+              break
+          elif [[ ! -s "$SOURCE/$SNAPSHOT/info.xml" ]]; then
+              echo "Warning: skipping source $SNAPSHOT due to invalid info.xml" >&2
+              continue
+          fi
+  
+          CLONE=0
+          if [[ ! -e "$TARGET/$SNAPSHOT" ]]; then
+              CLONE=1
+          elif [[ $ALL_ARE_BAD -eq 1 || ! -f "$TARGET/$SNAPSHOT/info.xml" ]]; then
+              echo -n "Warning: bad copy $SNAPSHOT (" >&2
+              [[ $ALL_ARE_BAD -eq 1 ]] && echo -n "bad chain" >&2 || echo -n "incomplete" >&2
+              echo "), recreating..." >&2
+  
+              cleanup "$SNAPSHOT"
+  
+              CLONE=1
+              ALL_ARE_BAD=1
+          fi
+  
+          if [[ $CLONE -eq 1 ]]; then
+              clone "$SNAPSHOT" "$PARENT"
+          elif [[ -z "$PARENT" ]]; then
+              echo "Initial snapshot present, all copies will be incremental" >&2
+          fi
+  
+          chmod 750 "$TARGET/$SNAPSHOT"
+          PARENT="$SNAPSHOT"
+      done
+  
+      [[ $RESET -eq 1 ]] && continue
+  
+      echo "Copies updated, cleaning up..." >&2
+      for SNAPSHOT in "''${EXISTENT[@]}"; do
+          FOUND=0
+          for KEEP in "''${SNAPSHOTS[@]}"; do
+              if [ "$KEEP" = "$SNAPSHOT" ]; then
+                  FOUND=1
+                  break
+              fi
+          done
+
+          [ -n "$FOUND" ] || cleanup "$SNAPSHOT"
+      done
+  
+      break
+  done
+  
+  echo "Done" >&2
+''
diff --git a/pkgs/btclone/default.nix b/pkgs/btclone/default.nix
new file mode 100644
index 0000000..bb207ef
--- /dev/null
+++ b/pkgs/btclone/default.nix
@@ -0,0 +1,6 @@
+{ btrfs-progs, pv, writeShellApplication, ... }:
+writeShellApplication {
+  name = "btclone";
+  runtimeInputs = [ btrfs-progs pv ];
+  text = import ./btclone.nix;
+}
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 5ee0a63..712242e 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -13,6 +13,7 @@ in {
     exclude = [ "config" ];
   });
 
+  btclone = callPackage ./btclone {};
   git-aliases = callPackage ./git-aliases.nix {};
   scripts = callPackage ./scripts {};
   tmux-lift = callPackage ./tmux-lift {};