master 4808c63d43f: Add Tramp method "apptainer"

[Michael Albinus]

branch: master
commit 4808c63d43f529f41aac2f2bb14df7ab8f882440
Author: Michael Albinus <michael.albinus@gmx.de>
Commit: Michael Albinus <michael.albinus@gmx.de>

    Add Tramp method "apptainer"
    
    * doc/misc/tramp.texi (Top, Configuration): Add "Optional methods".
    (Optional methods): New section.
    (Inline methods) <androidsu, toolbox, flatpak>: These are optional
    methods.
    (Inline methods) <apptainer>: Add.
    
    * etc/NEWS: New Tramp method "apptainer".
    Some Tramp methods are optional.
    Fix typos.
    
    * lisp/net/tramp-androidsu.el (tramp-enable-androidsu-method):
    New defun.  Call it when `system-type' is `android'.
    
    * lisp/net/tramp-container.el (tramp-apptainer-program): New defcustom.
    (tramp-apptainer-method): New defconst.
    (tramp-apptainer--completion-function)
    (tramp-enable-toolbox-method, tramp-enable-flatpak-method)
    (tramp-enable-apptainer-method): New defuns.
    
    * lisp/net/tramp.el (tramp-enable-method): New defun.
    
    * test/lisp/net/tramp-tests.el (tramp--test-container-p):
    Add "apptainer".
    (tramp--test-supports-processes-p): Extend function.
---
 doc/misc/tramp.texi          |  45 +++++++++-
 etc/NEWS                     |  61 +++++++------
 lisp/net/tramp-androidsu.el  |  32 ++++---
 lisp/net/tramp-container.el  | 203 +++++++++++++++++++++++++++++--------------
 lisp/net/tramp.el            |   9 ++
 test/lisp/net/tramp-tests.el |  12 ++-
 6 files changed, 249 insertions(+), 113 deletions(-)

diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index c87d0e70bb4..74516555a2c 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -119,6 +119,7 @@ Installing @value{tramp} with your Emacs
 
 Configuring @value{tramp} for use
 
+* Optional methods::            Optional methods which must be enabled first.
 * Connection types::            Types of connections to remote hosts.
 * Inline methods::              Inline methods.
 * External methods::            External methods.
@@ -685,6 +686,7 @@ to non-@code{nil}, @xref{Directory Variables, , , emacs}.
 
 
 @menu
+* Optional methods::            Optional methods which must be enabled first.
 * Connection types::            Types of connections to remote hosts.
 * Inline methods::              Inline methods.
 * External methods::            External methods.
@@ -718,6 +720,30 @@ on the remote host.
 @end menu
 
 
+@node Optional methods
+@section Optional methods which must be enabled first
+@cindex optional methods
+
+Not all methods are enabled by default after loading @value{tramp}.
+Some of them don't work on the local host.  Some of them are optional,
+and must be enabled if it is intended to use them.  For all methods
+described in this manual, it is indicated when the method is optional.
+
+@deffn Command tramp-enable-method method
+This command enables the optional method @var{method}, a string.  The
+command can be invoked interactively like @kbd{M-x tramp-enable-method
+@key{RET} toolbox @key{RET}}, with @option{toolbox} being an optional
+method.
+@end deffn
+
+If you want to enable an optional method permanently, add something
+like this to your @file{.emacs} file:
+
+@lisp
+(with-eval-after-load 'tramp (tramp-enable-method "toolbox"))
+@end lisp
+
+
 @node Connection types
 @section Types of connections to remote hosts
 @cindex connection types, overview
@@ -834,6 +860,9 @@ equivalent @option{androidsu} method is provided for that 
system with
 workarounds for its many idiosyncrasies, with the exception that
 multi-hops are unsupported.
 
+This is an optional method, @ref{Optional methods}.  It is enabled by
+default on @code{android} systems only.
+
 @item @option{sudo}
 @cindex method @option{sudo}
 @cindex @option{sudo} method
@@ -960,7 +989,8 @@ a container's name or ID, as returned by @samp{toolbox list 
-c}.
 Without a host name, the default Toolbox container for the host will
 be used.
 
-This method does not support user names.
+This is an optional method, @ref{Optional methods}.  It does not
+support user names.
 
 @item @option{flatpak}
 @cindex method @option{flatpak}
@@ -970,7 +1000,18 @@ Integration of Flatpak sandboxes.  The host name may be 
either an
 application ID, a sandbox instance ID, or a PID, as returned by
 @samp{flatpak ps}.
 
-This method does not support user names.
+This is an optional method, @ref{Optional methods}.  It does not
+support user names.
+
+@item @option{apptainer}
+@cindex method @option{apptainer}
+@cindex @option{apptainer} method
+
+Integration of Apptainer instances.  The host name is the instance
+name, as returned by @samp{apptainer instance list}.
+
+This is an optional method, @ref{Optional methods}.  It does not
+support user names.
 
 @end table
 
diff --git a/etc/NEWS b/etc/NEWS
index 456f9b8f8b8..abd879384d1 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -171,7 +171,7 @@ This user option controls outline visibility in the output 
buffer of
 *** 'C-h m' ('describe-mode') uses outlining by default.
 Set 'describe-mode-outline' to nil to get back the old behavior.
 
-** Outline Mode
+** Outline mode
 
 +++
 *** 'outline-minor-mode' is supported in tree-sitter major modes.
@@ -401,7 +401,7 @@ them.
 ** New optional argument for modifying directory-local variables.
 The commands 'add-dir-local-variable', 'delete-dir-local-variable' and
 'copy-file-locals-to-dir-locals' now take an optional prefix argument,
-to enter the file you want to modify.
+to enter the file name you want to modify.
 
 ** Emacs Server and Client
 
@@ -1051,7 +1051,12 @@ mode line.  'header' will display in the header line;
 ** Tramp
 
 +++
-*** New connection method "androidsu".
+*** Tramp methods can be optional.
+An optional connection method is not enabled by default.  The user must
+enable it explicitly by the 'tramp-enable-method' command.
+
++++
+*** New optional connection method "androidsu".
 This provides access to system files with elevated privileges granted by
 the idiosyncratic 'su' implementations and system utilities customary on
 Android.
@@ -1061,9 +1066,9 @@ Android.
 These are the external methods counterparts of "docker" and "podman".
 
 +++
-*** New connection methods "toolbox" and "flatpak".
-They allow accessing system containers provided by Toolbox or
-sandboxes provided by Flatpak.
+*** New optional connection methods "toolbox", "flatpak" and "apptainer".
+They allow accessing system containers provided by Toolbox, sandboxes
+provided by Flatpak, or instances managed by Apptainer.
 
 +++
 *** Connection method "kubernetes" supports now optional container name.
@@ -1138,7 +1143,7 @@ input, as the case may be.
 *** EWW text input fields and areas are now fields.
 In consequence, movement commands and OS input method features now
 recognize and confine their activities to the text input field around
-point.  See also (elisp)Fields.
+point.  See also the Info node "(elisp) Fields".
 
 +++
 *** 'eww-open-file' can now display the file in a new buffer.
@@ -1298,7 +1303,7 @@ the margin indicator.
 *** New user option 'flymake-autoresize-margins'.
 If non-nil, Flymake will resize the margins when 'flymake-mode' is
 turned on or off.
-Only relevant if `flymake-indicator-type` is set to `margins`.
+Only relevant if 'flymake-indicator-type' is set to 'margins'.
 
 +++
 *** New user option 'flymake-margin-indicator-position'.
@@ -1384,12 +1389,12 @@ when using the ':vc' keyword.
 ** Gnus
 
 +++
-*** New back end 'nnfeed'.
-This allows back end developers to easily create new back ends for web
-feeds, as inheriting back ends of 'nnfeed'.
+*** New backend 'nnfeed'.
+This allows backend developers to easily create new backends for web
+feeds, as inheriting backends of 'nnfeed'.
 
 +++
-*** New back end 'nnatom'.
+*** New backend 'nnatom'.
 This allow users to add Atom Syndication Format feeds to Gnus as
 servers.
 
@@ -1610,7 +1615,8 @@ macros with many lines, such as from 
'kmacro-edit-lossage'.
 The user option 'proced-auto-update-flag' can now be set to 2 additional
 values, which control automatic updates of Proced buffers that are not
 displayed in some window.
-** Kmacro Menu Mode
+
+** Kmacro Menu mode
 
 +++
 *** New mode 'kmacro-menu-mode' and new command 'list-keyboard-macros'.
@@ -1678,7 +1684,7 @@ options of GNU 'ls'.
 +++
 *** New user option 'widget-skip-inactive'.
 If non-nil, moving point forward or backward between widgets by typing
-TAB or S-TAB skips over inactive widgets.  The default value is nil.
+'TAB' or 'S-TAB' skips over inactive widgets.  The default value is nil.
 
 ** Miscellaneous
 
@@ -1694,7 +1700,7 @@ Now, calling '(thing-at-point 'url)' when point is on a 
bug reference
 will return the URL for that bug.
 
 +++
-*** New user option 'rcirc-log-time-format'
+*** New user option 'rcirc-log-time-format'.
 This allows for rcirc logs to use a custom timestamp format, than the
 chat buffers use by default.
 
@@ -1818,9 +1824,9 @@ various subparts (when 'interactive-form', 
'documentation', and
 ** 'define-globalized-minor-mode' requires that modes use 'run-mode-hooks'.
 Minor modes defined with 'define-globalized-minor-mode', such as
 'global-font-lock-mode', will not be enabled any more in those buffers
-whose major modes fails to use 'run-mode-hooks'.  Major modes defined
-with 'define-derived-mode' are not affected.  `run-mode-hooks` has been the
-recommended way to run major mode hooks since Emacs-22.
+whose major modes fail to use 'run-mode-hooks'.  Major modes defined
+with 'define-derived-mode' are not affected.  'run-mode-hooks' has been the
+recommended way to run major mode hooks since Emacs 22.
 
 ---
 ** Old derived.el functions removed.
@@ -1962,8 +1968,9 @@ arguments and its return type using the 'declare' macro.
 'interpreted-function' is the new type used for interpreted functions,
 and 'closure' is the common parent type of 'interpreted-function'
 and 'byte-code-function'.
-Those new types come with the associated new predicates
-'closurep' and `interpreted-function-p' as well as a new constructor
+
+Those new types come with the associated new predicates 'closurep' and
+`interpreted-function-p' as well as a new constructor
 'make-interpreted-closure'.
 
 ** New function 'help-fns-function-name'.
@@ -2023,9 +2030,9 @@ the Info node "(elisp) Handling Errors".
 +++
 ** Tooltips on fringes.
 It is now possible to provide tooltips on fringes by adding special text
-properties 'left-fringe-help' and 'right-fringe-help'.  See the "Special
-Properties" Info node in the Emacs Lisp Reference Manual for more
-details.
+properties 'left-fringe-help' and 'right-fringe-help'.  See the "(elisp)
+Special Properties" Info node in the Emacs Lisp Reference Manual for
+more details.
 
 +++
 ** New 'pop-up-frames' action alist entry for 'display-buffer'.
@@ -2594,7 +2601,7 @@ correctly UTF-8 encoded.
 *** The parser and encoder now accept arbitrarily large integers.
 Previously, they were limited to the range of signed 64-bit integers.
 
-** New tree-sitter functions and variables for defining and using "things".
+** New tree-sitter functions and variables for defining and using "things"
 
 +++
 *** New variable 'treesit-thing-settings'.
@@ -2618,7 +2625,7 @@ accept more kinds of predicates.  Lisp programs can now 
use thing
 symbols (defined in 'treesit-thing-settings') and any thing definitions
 for the predicate argument.
 
-** Other tree-sitter function and variable changes.
+** Other tree-sitter function and variable changes
 
 +++
 *** 'treesit-parser-list' now takes additional optional arguments.
@@ -2629,13 +2636,11 @@ all parsers, but rather "all parsers with no tags".
 
 +++
 *** New function 'treesit-parser-changed-ranges'.
-
 This function returns buffer regions that are affected by the last
 buffer edits.
 
 *** New function 'treesit-add-font-lock-rules'.
-
-This function helps user to add custom font-lock rules to a tree-sitter
+This function helps users to add custom font-lock rules to a tree-sitter
 major mode.
 
 ---
diff --git a/lisp/net/tramp-androidsu.el b/lisp/net/tramp-androidsu.el
index aa7871e6a33..3dcee8e2f8a 100644
--- a/lisp/net/tramp-androidsu.el
+++ b/lisp/net/tramp-androidsu.el
@@ -77,19 +77,25 @@ may edit files belonging to any and all applications."
   "Name of the local temporary directory on Android.")
 
 ;;;###tramp-autoload
-(tramp--with-startup
- (add-to-list 'tramp-methods
-             `(,tramp-androidsu-method
-                (tramp-login-program       "su")
-                (tramp-login-args          (("-") ("%u")))
-                (tramp-remote-shell        ,tramp-androidsu-local-shell-name)
-                (tramp-remote-shell-login  ("-l"))
-                (tramp-remote-shell-args   ("-c"))
-                (tramp-tmpdir              
,tramp-androidsu-local-tmp-directory)
-                (tramp-connection-timeout  10)
-                (tramp-shell-name         ,tramp-androidsu-local-shell-name)))
- (add-to-list 'tramp-default-user-alist
-              `(,tramp-androidsu-method nil ,tramp-root-id-string)))
+(defun tramp-enable-androidsu-method ()
+  "Enable \"androidsu\" method."
+  (add-to-list 'tramp-methods
+              `(,tramp-androidsu-method
+                 (tramp-login-program       "su")
+                 (tramp-login-args          (("-") ("%u")))
+                 (tramp-remote-shell        ,tramp-androidsu-local-shell-name)
+                 (tramp-remote-shell-login  ("-l"))
+                 (tramp-remote-shell-args   ("-c"))
+                 (tramp-tmpdir              
,tramp-androidsu-local-tmp-directory)
+                 (tramp-connection-timeout  10)
+                 (tramp-shell-name        ,tramp-androidsu-local-shell-name)))
+
+  (add-to-list 'tramp-default-user-alist
+               `(,tramp-androidsu-method nil ,tramp-root-id-string)))
+
+;;;###tramp-autoload
+(when (eq system-type 'android)
+  (tramp-enable-androidsu-method))
 
 (defvar android-use-exec-loader) ; androidfns.c.
 
diff --git a/lisp/net/tramp-container.el b/lisp/net/tramp-container.el
index 30639cbeb85..7559f958838 100644
--- a/lisp/net/tramp-container.el
+++ b/lisp/net/tramp-container.el
@@ -83,6 +83,15 @@
 ;; Where:
 ;;     SANDBOX is the running sandbox to connect to.
 ;;             It could be an application ID, an instance ID, or a PID.
+;;
+;;
+;;
+;; Open a file on a running Apptainer instance:
+;;
+;;     C-x C-f /apptainer:INSTANCE:/path/to/file
+;;
+;; Where:
+;;     INSTANCE        is the running instance to connect to.
 
 ;;; Code:
 
@@ -142,6 +151,14 @@ If it is nil, the default context will be used."
   :type '(choice (const "flatpak")
                  (string)))
 
+;;;###tramp-autoload
+(defcustom tramp-apptainer-program "apptainer"
+  "Name of the Apptainer client program."
+  :group 'tramp
+  :version "30.1"
+  :type '(choice (const "apptainer")
+                 (string)))
+
 ;;;###tramp-autoload
 (defconst tramp-docker-method "docker"
   "Tramp method name to use to connect to Docker containers.")
@@ -172,6 +189,10 @@ This is for out-of-band connections.")
 (defconst tramp-flatpak-method "flatpak"
   "Tramp method name to use to connect to Flatpak sandboxes.")
 
+;;;###tramp-autoload
+(defconst tramp-apptainer-method "apptainer"
+  "Tramp method name to use to connect to Apptainer instances.")
+
 ;;;###tramp-autoload
 (defmacro tramp-skeleton-completion-function (method &rest body)
   "Skeleton for `tramp-*-completion-function' with multi-hop support.
@@ -373,6 +394,28 @@ see its function help for a description of the format."
                        lines)))
       (mapcar (lambda (name) (list nil name)) (delq nil names)))))
 
+;;;###tramp-autoload
+(defun tramp-apptainer--completion-function (method)
+  "List Apptainer instances available for connection.
+
+This function is used by `tramp-set-completion-function', please
+see its function help for a description of the format."
+  (tramp-skeleton-completion-function method
+    (when-let ((raw-list
+               (shell-command-to-string (concat program " instance list")))
+              ;; Ignore header line.
+               (lines (cdr (split-string raw-list "\n" 'omit)))
+               (names (mapcar
+                      (lambda (line)
+                        (when (string-match
+                               (rx bol (group (1+ (not space)))
+                                   (1+ space) (1+ (not space))
+                                   (1+ space) (1+ (not space)))
+                               line)
+                          (match-string 1 line)))
+                       lines)))
+      (mapcar (lambda (name) (list nil name)) (delq nil names)))))
+
 ;;;###tramp-autoload
 (defvar tramp-default-remote-shell) ;; Silence byte compiler.
 
@@ -453,29 +496,9 @@ see its function help for a description of the format."
                 (tramp-remote-shell-login ("-l"))
                 (tramp-remote-shell-args ("-i" "-c"))))
 
- (add-to-list 'tramp-methods
-             `(,tramp-toolbox-method
-               (tramp-login-program ,tramp-toolbox-program)
-               (tramp-login-args (("run")
-                                  ("-c" "%h")
-                                  ("%l")))
-               (tramp-direct-async (,tramp-default-remote-shell "-c"))
-               (tramp-remote-shell ,tramp-default-remote-shell)
-               (tramp-remote-shell-login ("-l"))
-               (tramp-remote-shell-args ("-c"))))
-
- (add-to-list 'tramp-default-host-alist `(,tramp-toolbox-method nil ""))
-
- (add-to-list 'tramp-methods
-             `(,tramp-flatpak-method
-               (tramp-login-program ,tramp-flatpak-program)
-               (tramp-login-args (("enter")
-                                  ("%h")
-                                  ("%l")))
-               (tramp-direct-async (,tramp-default-remote-shell "-c"))
-               (tramp-remote-shell ,tramp-default-remote-shell)
-               (tramp-remote-shell-login ("-l"))
-               (tramp-remote-shell-args ("-c"))))
+ (add-to-list 'tramp-completion-multi-hop-methods tramp-docker-method)
+ (add-to-list 'tramp-completion-multi-hop-methods tramp-podman-method)
+ (add-to-list 'tramp-completion-multi-hop-methods tramp-kubernetes-method)
 
  (tramp-set-completion-function
   tramp-docker-method
@@ -495,53 +518,99 @@ see its function help for a description of the format."
 
  (tramp-set-completion-function
   tramp-kubernetes-method
-  `((tramp-kubernetes--completion-function ,tramp-kubernetes-method)))
+  `((tramp-kubernetes--completion-function ,tramp-kubernetes-method))))
 
- (tramp-set-completion-function
-  tramp-toolbox-method
-  `((tramp-toolbox--completion-function ,tramp-toolbox-method)))
+;;;###tramp-autoload
+(defun tramp-enable-toolbox-method ()
+  "Enable connection to Toolbox containers."
+  (add-to-list 'tramp-methods
+              `(,tramp-toolbox-method
+                (tramp-login-program ,tramp-toolbox-program)
+                (tramp-login-args (("run")
+                                   ("-c" "%h")
+                                   ("%l")))
+                (tramp-direct-async (,tramp-default-remote-shell "-c"))
+                (tramp-remote-shell ,tramp-default-remote-shell)
+                (tramp-remote-shell-login ("-l"))
+                (tramp-remote-shell-args ("-c"))))
+
+  (add-to-list 'tramp-default-host-alist `(,tramp-toolbox-method nil ""))
+  (add-to-list 'tramp-completion-multi-hop-methods tramp-toolbox-method)
+
+  (tramp-set-completion-function
+   tramp-toolbox-method
+   `((tramp-toolbox--completion-function ,tramp-toolbox-method))))
 
- (tramp-set-completion-function
-  tramp-flatpak-method
-  `((tramp-flatpak--completion-function ,tramp-flatpak-method)))
+;;;###tramp-autoload
+(defun tramp-enable-flatpak-method ()
+  "Enable connection to Flatpak sandboxes."
+  (add-to-list 'tramp-methods
+              `(,tramp-flatpak-method
+                (tramp-login-program ,tramp-flatpak-program)
+                (tramp-login-args (("enter")
+                                   ("%h")
+                                   ("%l")))
+                (tramp-direct-async (,tramp-default-remote-shell "-c"))
+                (tramp-remote-shell ,tramp-default-remote-shell)
+                (tramp-remote-shell-login ("-l"))
+                (tramp-remote-shell-args ("-c"))))
+
+  (add-to-list 'tramp-completion-multi-hop-methods tramp-flatpak-method)
+
+  (tramp-set-completion-function
+   tramp-flatpak-method
+   `((tramp-flatpak--completion-function ,tramp-flatpak-method))))
 
- (add-to-list 'tramp-completion-multi-hop-methods tramp-docker-method)
- (add-to-list 'tramp-completion-multi-hop-methods tramp-podman-method)
- (add-to-list 'tramp-completion-multi-hop-methods tramp-kubernetes-method)
- (add-to-list 'tramp-completion-multi-hop-methods tramp-toolbox-method)
- (add-to-list 'tramp-completion-multi-hop-methods tramp-flatpak-method)
-
- ;; Default connection-local variables for Tramp.
-
- (defconst tramp-kubernetes-connection-local-default-variables
-   '((tramp-config-check . tramp-kubernetes--current-context-data)
-     ;; This variable will be eval'ed in `tramp-expand-args'.
-     (tramp-extra-expand-args
-      . (?a (tramp-kubernetes--container (car tramp-current-connection))
-        ?h (tramp-kubernetes--pod (car tramp-current-connection))
-        ?x (tramp-kubernetes--context-namespace
-            (car tramp-current-connection)))))
-   "Default connection-local variables for remote kubernetes connections.")
-
- (connection-local-set-profile-variables
-  'tramp-kubernetes-connection-local-default-profile
-  tramp-kubernetes-connection-local-default-variables)
-
- (connection-local-set-profiles
-  `(:application tramp :protocol ,tramp-kubernetes-method)
-  'tramp-kubernetes-connection-local-default-profile)
-
- (defconst tramp-flatpak-connection-local-default-variables
-   `((tramp-remote-path  . ,(cons "/app/bin" tramp-remote-path)))
-   "Default connection-local variables for remote flatpak connections.")
-
- (connection-local-set-profile-variables
-  'tramp-flatpak-connection-local-default-profile
-  tramp-flatpak-connection-local-default-variables)
-
- (connection-local-set-profiles
-  `(:application tramp :protocol ,tramp-flatpak-method)
-  'tramp-flatpak-connection-local-default-profile))
+;;;###tramp-autoload
+(defun tramp-enable-apptainer-method ()
+  "Enable connection to Apptainer instances."
+  (add-to-list 'tramp-methods
+              `(,tramp-apptainer-method
+                (tramp-login-program ,tramp-apptainer-program)
+                (tramp-login-args (("shell")
+                                   ("instance://%h")
+                                   ("%h"))) ; Needed for multi-hop check.
+                (tramp-remote-shell ,tramp-default-remote-shell)
+                (tramp-remote-shell-login ("-l"))
+                (tramp-remote-shell-args ("-c"))))
+
+  (add-to-list 'tramp-completion-multi-hop-methods tramp-apptainer-method)
+
+  (tramp-set-completion-function
+   tramp-apptainer-method
+   `((tramp-apptainer--completion-function ,tramp-apptainer-method))))
+
+;; Default connection-local variables for Tramp.
+
+(defconst tramp-kubernetes-connection-local-default-variables
+  '((tramp-config-check . tramp-kubernetes--current-context-data)
+    ;; This variable will be eval'ed in `tramp-expand-args'.
+    (tramp-extra-expand-args
+     . (?a (tramp-kubernetes--container (car tramp-current-connection))
+       ?h (tramp-kubernetes--pod (car tramp-current-connection))
+       ?x (tramp-kubernetes--context-namespace
+           (car tramp-current-connection)))))
+  "Default connection-local variables for remote kubernetes connections.")
+
+(connection-local-set-profile-variables
+ 'tramp-kubernetes-connection-local-default-profile
+ tramp-kubernetes-connection-local-default-variables)
+
+(connection-local-set-profiles
+ `(:application tramp :protocol ,tramp-kubernetes-method)
+ 'tramp-kubernetes-connection-local-default-profile)
+
+(defconst tramp-flatpak-connection-local-default-variables
+  `((tramp-remote-path  . ,(cons "/app/bin" tramp-remote-path)))
+  "Default connection-local variables for remote flatpak connections.")
+
+(connection-local-set-profile-variables
+ 'tramp-flatpak-connection-local-default-profile
+ tramp-flatpak-connection-local-default-variables)
+
+(connection-local-set-profiles
+ `(:application tramp :protocol ,tramp-flatpak-method)
+ 'tramp-flatpak-connection-local-default-profile)
 
 (add-hook 'tramp-unload-hook
          (lambda ()
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 4c62d1d9f39..f6d02847927 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -1460,6 +1460,15 @@ calling HANDLER.")
 
 ;;; Internal functions which must come first:
 
+(defun tramp-enable-method (method)
+  "Enable optional METHOD if possible."
+  (interactive "Mmethod: ")
+  (when-let (((not (assoc method tramp-methods)))
+            (fn (intern (format "tramp-enable-%s-method" method)))
+            ((functionp fn)))
+    (funcall fn)
+    (message "Tramp method \"%s\" enabled" method)))
+
 ;; Conversion functions between external representation and
 ;; internal data structure.  Convenience functions for internal
 ;; data structure.
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index cdd2a1efdb2..68095c93a00 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -7064,7 +7064,7 @@ This is used in tests which we don't want to tag
   "Check, whether a container method is used.
 This does not support some special file names."
   (string-match-p
-   (rx bol (| "docker" "podman"))
+   (rx bol (| "docker" "podman" "apptainer"))
    (file-remote-p ert-remote-temporary-file-directory 'method)))
 
 (defun tramp--test-container-oob-p ()
@@ -7233,8 +7233,14 @@ This requires restrictions of file name syntax."
 
 (defun tramp--test-supports-processes-p ()
   "Return whether the method under test supports external processes."
-  (and (or (tramp--test-adb-p) (tramp--test-sh-p) (tramp--test-sshfs-p))
-       (not (tramp--test-crypt-p))))
+  ;; We use it to enable/disable tests in a given test run, for
+  ;; example for remote processes on MS Windows.
+  (if (tramp-connection-property-p
+       tramp-test-vec "tramp--test-supports-processes-p")
+      (tramp-get-connection-property
+       tramp-test-vec "tramp--test-supports-processes-p")
+    (and (or (tramp--test-adb-p) (tramp--test-sh-p) (tramp--test-sshfs-p))
+        (not (tramp--test-crypt-p)))))
 
 (defun tramp--test-supports-set-file-modes-p ()
   "Return whether the method under test supports setting file modes."