extension-release: search for other files if expected name not found

In some cases image names are unpredictable - some orchestrators/deployment
tools like to mangle names to suit their internal formats. In these cases,
the requirement that the extension-release file matches exactly the image
name where it's contained cannot work.

Allow falling back to loading the first regular file which name starts with
'extension-release' located in /usr/lib/extension-release.d/ and tagged with
a user.extension-release.strict extended attribute with a true value, if the
one with the expected name cannot be found.

test/test-functions

@@ -626,8 +626,9 @@ EOF
 
         export initdir="$TESTDIR/app1"
         mkdir -p "$initdir/usr/lib/extension-release.d" "$initdir/usr/lib/systemd/system" "$initdir/opt"
-        grep "^ID=" "$os_release" >"$initdir/usr/lib/extension-release.d/extension-release.app1"
-        echo "${version_id}" >>"$initdir/usr/lib/extension-release.d/extension-release.app1"
+        grep "^ID=" "$os_release" >"$initdir/usr/lib/extension-release.d/extension-release.app2"
+        echo "${version_id}" >>"$initdir/usr/lib/extension-release.d/extension-release.app2"
+        setfattr -n user.extension-release.strict -v false "$initdir/usr/lib/extension-release.d/extension-release.app2"
         cat >"$initdir/usr/lib/systemd/system/app1.service" <<EOF
 [Service]
 Type=oneshot
@@ -638,7 +639,7 @@ EOF
 #!/bin/bash
 set -e
 test -e /usr/lib/os-release
-cat /usr/lib/extension-release.d/extension-release.app1
+cat /usr/lib/extension-release.d/extension-release.app2
 EOF
         chmod +x "$initdir/opt/script1.sh"
         echo MARKER=1 >"$initdir/usr/lib/systemd/system/other_file"

test/units/testsuite-29.sh

@@ -5,6 +5,11 @@ set -eux
 set -o pipefail
 
 export SYSTEMD_LOG_LEVEL=debug
+mkdir -p /run/systemd/system/systemd-portabled.service.d/
+cat <<EOF >/run/systemd/system/systemd-portabled.service.d/override.conf
+[Service]
+Environment=SYSTEMD_LOG_LEVEL=debug
+EOF
 
 portablectl attach --now --runtime /usr/share/minimal_0.raw app0
 
@@ -63,24 +68,31 @@ portablectl detach --now --enable --runtime /tmp/minimal_1 app0
 
 portablectl list | grep -q -F "No images."
 
-root="/usr/share/minimal_0.raw"
-app1="/usr/share/app1.raw"
+portablectl attach --now --runtime --extension /usr/share/app0.raw /usr/share/minimal_0.raw app0
 
-portablectl attach --now --runtime --extension ${app1} ${root} app1
+systemctl is-active app0.service
+
+portablectl reattach --now --runtime --extension /usr/share/app0.raw /usr/share/minimal_1.raw app0
+
+systemctl is-active app0.service
+
+portablectl detach --now --runtime --extension /usr/share/app0.raw /usr/share/minimal_1.raw app0
+
+portablectl attach --now --runtime --extension /usr/share/app1.raw /usr/share/minimal_0.raw app1
 
 systemctl is-active app1.service
 
-portablectl reattach --now --runtime --extension ${app1} ${root} app1
+portablectl reattach --now --runtime --extension /usr/share/app1.raw /usr/share/minimal_1.raw app1
 
 systemctl is-active app1.service
 
-portablectl detach --now --runtime --extension ${app1} ${root} app1
+portablectl detach --now --runtime --extension /usr/share/app1.raw /usr/share/minimal_1.raw app1
 
 # portablectl also works with directory paths rather than images
 
 mkdir /tmp/rootdir /tmp/app1 /tmp/overlay
-mount ${app1} /tmp/app1
-mount ${root} /tmp/rootdir
+mount /usr/share/app1.raw /tmp/app1
+mount /usr/share/minimal_0.raw /tmp/rootdir
 mount -t overlay overlay -o lowerdir=/tmp/app1:/tmp/rootdir /tmp/overlay
 
 portablectl attach --copy=symlink --now --runtime /tmp/overlay app1

test/units/testsuite-50.sh

@@ -235,7 +235,7 @@ systemd-run -P --property ExtensionImages=/usr/share/app0.raw --property RootIma
 systemd-run -P --property ExtensionImages=/usr/share/app0.raw --property RootImage="${image}.raw" cat /usr/lib/systemd/system/some_file | grep -q -F "MARKER=1"
 systemd-run -P --property ExtensionImages="/usr/share/app0.raw /usr/share/app1.raw" --property RootImage="${image}.raw" cat /opt/script0.sh | grep -q -F "extension-release.app0"
 systemd-run -P --property ExtensionImages="/usr/share/app0.raw /usr/share/app1.raw" --property RootImage="${image}.raw" cat /usr/lib/systemd/system/some_file | grep -q -F "MARKER=1"
-systemd-run -P --property ExtensionImages="/usr/share/app0.raw /usr/share/app1.raw" --property RootImage="${image}.raw" cat /opt/script1.sh | grep -q -F "extension-release.app1"
+systemd-run -P --property ExtensionImages="/usr/share/app0.raw /usr/share/app1.raw" --property RootImage="${image}.raw" cat /opt/script1.sh | grep -q -F "extension-release.app2"
 systemd-run -P --property ExtensionImages="/usr/share/app0.raw /usr/share/app1.raw" --property RootImage="${image}.raw" cat /usr/lib/systemd/system/other_file | grep -q -F "MARKER=1"
 cat >/run/systemd/system/testservice-50e.service <<EOF
 [Service]