Do not hardcode "/bin/sh" in compile. Bug#24338, Bug#29723

* doc/emacs/custom.texi (Connection Variables): New node.

* doc/emacs/emacs.texi (Top): Add entry for Connection Variables.

* doc/emacs/misc.texi (Single Shell): Mention default value for
remote buffers.

* doc/lispref/variables.texi (Connection Local Variables):
Describe `with-connection-local-variables' instead of
`with-connection-local-profiles'.

* doc/misc/tramp.texi (Remote processes): Refer to Emacs manual.
Mention default connection-local settings for `shell-file-name'
and `shell-command-switch'.

* etc/NEWS: Mention connection-local variables changes.

* lisp/files-x.el (hack-connection-local-variables):
Push connection-local variables to `file-local-variables-alist'.
(connection-local-criteria-for-default-directory): New defsubst.
(with-connection-local-variables): Rename from
`with-connection-local-profiles'.  Adapt implementation.

* lisp/files.el (hack-local-variables):
Call `hack-connection-local-variables'.

* lisp/shell.el (shell): Use `with-connection-local-variables'.

* lisp/subr.el (start-file-process-shell-command):
* lisp/progmodes/compile.el (compilation-start):
Use `with-connection-local-variables'.  Do not set "/bin/sh" for
remote buffers, trust settings of `shell-file-name'.  (Bug#24338),
(Bug#29723)

* lisp/net/ange-ftp.el (ange-ftp-compress, ange-ftp-uncompress):
Use `shell-command-switch'.

* lisp/net/tramp-adb.el (tramp-adb-connection-local-default-profile):
New defvar.  Add it to connection-local profiles after loading "shell".

* lisp/net/tramp-integration.el (tramp-compat): Require tramp-compat.
(tramp-compat-exec-path): Do not declare anymore.
(tramp-connection-local-safe-shell-file-names): New defvar.
(tramp-connection-local-default-profile): New defconst.  Activate
it after loading "shell".
(shell-file-name, shell-command-switch): Add safe-local-variable
property.

* lisp/net/tramp-sh.el (tramp-display-escape-sequence-regexp):
Add tramp-autoload cookie.

* test/lisp/files-x-tests.el (remote-shell-file-name):
Add safe-local-variable property to remote-* variables.
(tramp-connection-local-default-profile): Declare.
(files-x-test-with-connection-local-variables):
Rename from `files-x-test-with-connection-local-profiles'.  Adapt
implementation.

* test/lisp/net/tramp-tests.el
(tramp-test34-connection-local-variables): New test.
(tramp-test34-explicit-shell-file-name): Run it also for tramp-adb.
Bind connection-local-{profile,criteria}-alist.  Use tramp-adb
specific `shell-file-name'.  Add safe-local-variable property to
`explicit-shell-file-name' and `explicit-sh-args'.

1 files changed, 33 insertions, 1 deletions

diff --git a/lisp/net/tramp-integration.el b/lisp/net/tramp-integration.el
index 2a461763480..946d7f8cbab 100644
--- a/lisp/net/tramp-integration.el
+++ b/lisp/net/tramp-integration.el
@@ -27,9 +27,10 @@
 
 ;;; Code:
 
+(require 'tramp-compat)
+
 ;; Pacify byte-compiler.
 (require 'cl-lib)
-(declare-function tramp-compat-exec-path "tramp")
 (declare-function tramp-dissect-file-name "tramp")
 (declare-function tramp-file-name-equal-p "tramp")
 (declare-function tramp-tramp-file-p "tramp")
@@ -170,6 +171,37 @@ NAME must be equal to `tramp-current-connection'."
 		 (remove-hook 'tramp-cleanup-all-connections-hook
 			      #'tramp-recentf-cleanup-all)))))
 
+;;; Default connection-local variables for Tramp:
+
+;;;###tramp-autoload
+(defvar tramp-connection-local-safe-shell-file-names nil
+  "List of safe `shell-file-name' values for remote hosts.")
+(add-to-list 'tramp-connection-local-safe-shell-file-names "/bin/sh")
+
+(defconst tramp-connection-local-default-profile
+  '((shell-file-name . "/bin/sh")
+    (shell-command-switch . "-c"))
+  "Default connection-local variables for remote connections.")
+(put 'shell-file-name 'safe-local-variable
+     (lambda (item)
+       (and (stringp item)
+	    (member item tramp-connection-local-safe-shell-file-names))))
+(put 'shell-command-switch 'safe-local-variable
+     (lambda (item) (and (stringp item) (string-equal item "-c"))))
+
+;; `connection-local-set-profile-variables' and
+;; `connection-local-set-profiles' exists since Emacs 26.1.
+(eval-after-load "shell"
+  '(progn
+     (tramp-compat-funcall
+      'connection-local-set-profile-variables
+      'tramp-connection-local-default-profile
+      tramp-connection-local-default-profile)
+     (tramp-compat-funcall
+      'connection-local-set-profiles
+      `(:application tramp)
+      'tramp-connection-local-default-profile)))
+
 (add-hook 'tramp-unload-hook
 	  (lambda () (unload-feature 'tramp-integration 'force)))