From 362dd9f4432417929614f86dcc670146e963a0c5 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Tue, 6 Jun 2023 08:02:33 -0400
Subject: detect rootfs path and mark it with /./

---
 list-all-subvolumes | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/list-all-subvolumes b/list-all-subvolumes
index 2acf772..ec042c7 100755
--- a/list-all-subvolumes
+++ b/list-all-subvolumes
@@ -7,15 +7,18 @@ list_all_subvolumes()
     for dev in $(list_btrfs)
     do
         [ -b "$dev" ] || return
-        d=btrfs/$$/$(systemd-escape "$dev")
+        d=btrfs/pid-$$/$(systemd-escape "$dev")
         (
             cd /run
             mkdir -p "$d" || exit
             trap 'umount "$d"; rmdir -p "$d" 2>/dev/null' EXIT
-            set -x
-            mountpoint -q "$d" || mount -o ro,subvol=/ "$dev" "$d" || return
-            btrfs subvolume list "$@" "$d"
-        ) | extract_subvolume_path "${d##*/}" || return
+            root=
+            (
+                set -x
+                mountpoint -q "$d" || mount -o ro,subvol=/ "$dev" "$d" || return
+                btrfs subvolume list "$@" "$d"
+            ) | extract_subvolume_path "/run/$d" || return
+        )
     done
 }
 
@@ -25,7 +28,19 @@ extract_subvolume_path()
     do
         path=${REPLY#* path }
         [ "$path" != "$REPLY" ]
-        printf '%s/%s\n' "$1" "${path#<FS_TREE>/}"
+        path=${path#<FS_TREE>/}
+
+        abspath=$1/$path
+        [ -d "$abspath" ] || exit
+
+        if [ ! "$root" -a "$abspath" -ef / ]
+        then
+            root=$path
+        fi
+        case "$path" in
+            "$root" | "$root"/*) path=$root/.${path#$root} ;;
+        esac
+        printf '%s//%s\n' "${1##*/}" "$path"
     done
 }
 
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