master c6e079ae15: Support remote home directories via connection property

[Michael Albinus]

branch: master
commit c6e079ae15002268d90869a43f66d962175e4cdb
Author: Michael Albinus <michael.albinus@gmx.de>
Commit: Michael Albinus <michael.albinus@gmx.de>

    Support remote home directories via connection property
    
    * doc/misc/tramp.texi (Home directories): New section.
    (Top, Usage): Add it to the menue.
    (Predefined connection information): Mention "~".
    (Multi-hops, File name syntax): Fix typos.
    
    * lisp/net/tramp.el (tramp-handle-expand-file-name): Check for
    remote home directory.  (Bug#53847)
---
 doc/misc/tramp.texi | 83 +++++++++++++++++++++++++++++++++++++++++++++++++----
 lisp/net/tramp.el   | 11 +++++++
 2 files changed, 88 insertions(+), 6 deletions(-)

diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index 20e6ee0bef..62bcf9c73b 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -157,6 +157,7 @@ Using @value{tramp}
 @end ifset
 * File name completion::        File name completion.
 * Ad-hoc multi-hops::           Declaring multiple hops in the file name.
+* Home directories::            Expanding @file{~} to home directory.
 * Remote processes::            Integration with other Emacs packages.
 * Cleanup remote connections::  Cleanup remote connections.
 * Renaming remote files::       Renaming remote files.
@@ -1663,7 +1664,7 @@ local one, first connect via @command{ssh}, and then apply
 (add-to-list 'tramp-default-proxies-alist
              '(nil "\\`root\\'" "@trampfn{ssh,%h,}"))
 (add-to-list 'tramp-default-proxies-alist
-             '((regexp-quote (system-name)) nil nil))
+             `(,(regexp-quote (system-name)) nil nil))
 @end group
 @end lisp
 @end defopt
@@ -2176,6 +2177,14 @@ reestablished.  A value of @code{nil} disables this 
feature.  Most of
 the methods do not set this property except the @option{sudo} and
 @option{doas} methods, which use predefined values.
 
+@item @t{"~"}@*
+@t{"~user"}
+
+This is the home directory on the remote host.  Setting this
+connection property helps especially for methods which cannot expand
+to a remote home directory, like @option{adb}, @option{rclone} and
+@option{sshfs}.  @ref{Home directories} for an example.
+
 @item @t{"tmpdir"}
 
 The temporary directory on the remote host.  If not specified, the
@@ -3252,6 +3261,7 @@ is a feature of Emacs that may cause missed prompts when 
using
 @end ifset
 * File name completion::        File name completion.
 * Ad-hoc multi-hops::           Declaring multiple hops in the file name.
+* Home directories::            Expanding @file{~} to home directory.
 * Remote processes::            Integration with other Emacs packages.
 * Cleanup remote connections::  Cleanup remote connections.
 * Renaming remote files::       Renaming remote files.
@@ -3267,24 +3277,25 @@ is a feature of Emacs that may cause missed prompts 
when using
 @file{@trampfn{method,host,/path/to/file}} opens file @var{/path/to/file}
 on the remote host @var{host}, using the method @var{method}.
 
+@c We cannot use @trampfn{} in @item.
 @table @file
-@item @trampfn{ssh,melancholia,.emacs}
+@item @value{prefix}ssh@value{postfixhop}melancholia@value{postfix}.emacs
 For the file @file{.emacs} located in the home directory, on the host
 @code{melancholia}, using method @code{ssh}.
 
-@item @trampfn{ssh,melancholia.danann.net,.emacs}
+@item 
@value{prefix}ssh@value{postfixhop}melancholia.danann.net@value{postfix}.emacs
 For the file @file{.emacs} specified using the fully qualified domain name of
 the host.
 
-@item @trampfn{ssh,melancholia,~/.emacs}
+@item @value{prefix}ssh@value{postfixhop}melancholia@value{postfix}~/.emacs
 For the file @file{.emacs} specified using the @file{~}, which is expanded.
 
-@item @trampfn{ssh,melancholia,~daniel/.emacs}
+@item 
@value{prefix}ssh@value{postfixhop}melancholia@value{postfix}~daniel/.emacs
 For the file @file{.emacs} located in @code{daniel}'s home directory
 on the host, @code{melancholia}.  The @file{~<user>} construct is
 expanded to the home directory of that user on the remote host.
 
-@item @trampfn{ssh,melancholia,/etc/squid.conf}
+@item 
@value{prefix}ssh@value{postfixhop}melancholia@value{postfix}/etc/squid.conf
 For the file @file{/etc/squid.conf} on the host @code{melancholia}.
 
 @end table
@@ -3534,6 +3545,66 @@ file name is equivalent to the previous example:
 @samp{@trampfn{ssh@value{postfixhop}remotehost|su,,}}.
 
 
+@node Home directories
+@section Expanding @file{~} to home directory
+
+Home directories on remote hosts can be typed as tilde @file{~}.  If
+possible, they are expanded to the remote user's home directory on the
+remote host.  Example:
+
+@example
+@group
+@trampfn{ssh,user@@host,~}
+@result{} @trampfn{ssh,user@@host,/home/user}
+@end group
+@end example
+
+This works in general for @option{ssh}-like methods, and for
+@option{sudoedit}.  These methods allow also the home directory
+expansion for another user, like
+
+@example
+@group
+@trampfn{sudoedit,,~otheruser}
+@result{} @trampfn{sudoedit,root@@localhost,/home/otheruser}
+@end group
+@end example
+
+For other methods, a home directory can be expanded only if supported.
+This happens for example for the @option{sftp} method.  Methods, which
+require a share directory in the remote file name (@option{afp},
+@option{smb}), use the value of this share directory as home
+directory:
+
+@example
+@group
+@trampfn{smb,user@@host,~}
+@result{} @trampfn{smb,user@@host,/share}
+@end group
+@end example
+
+Since Tramp cannot know in advance which share directory is intended
+to use, this expansion can be applied only when a share directory has
+been used already.
+
+The methods @option{adb}, @option{rclone} and @option{sshfs} do not
+support home directory expansion at all.  However, @value{tramp} keeps
+the home directory in the cache.  Therefore, those methods could be
+configured to expand a home directory via a connection property,
+@xref{Predefined connection information}.  Example:
+
+@lisp
+@group
+(add-to-list 'tramp-connection-properties
+             (list (regexp-quote 
"@trampfn{sshfs,user@@randomhost.your.domain,}")
+                   "~user" "/home/user"))
+@end group
+@end lisp
+
+When your remote file name does not contain a @samp{user} part, the
+connection property @t{"~"} must be used instead.
+
+
 @node Remote processes
 @section Integration with other Emacs packages
 @cindex @code{compile}
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 8f54f96573..49778cbfee 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -3501,6 +3501,17 @@ Let-bind it when necessary.")
     (with-parsed-tramp-file-name name nil
       (unless (tramp-run-real-handler #'file-name-absolute-p (list localname))
        (setq localname (concat "/" localname)))
+      ;; Expand tilde.  Usually, the methods applying this handler do
+      ;; not support tilde expansion.  But users could declare a
+      ;; respective connection property.  (Bug#53847)
+      (when (string-match "\\`~\\([^/]*\\)\\(.*\\)\\'" localname)
+       (let ((uname (match-string 1 localname))
+             (fname (match-string 2 localname))
+             hname)
+         (when (zerop (length uname))
+           (setq uname user))
+         (when (setq hname (tramp-get-home-directory v uname))
+           (setq localname (concat hname fname)))))
       ;; Tilde expansion is not possible.
       (when (and (not tramp-tolerate-tilde)
                 (string-match-p "\\`\\(~[^/]*\\)\\(.*\\)\\'" localname))