Expand host names in Tramp's ad-hoc multi-hop file names

* doc/misc/tramp.texi (Quick Start Guide): Improve wording.
(Change file name syntax): Say, that `tramp-file-name-regexp' is
not constant.
(Ad-hoc multi-hops): Explain host name expansion.

* etc/NEWS: Mention that host names in Tramp ad-hoc multi-hop file
names must match the previous hop for methods like "su" or "sudo".
Fix typos.

* lisp/net/tramp.el (tramp-find-method, tramp-find-user):
Adapt docstring.
(tramp-find-host): Mark default value.
(tramp-dissect-file-name): Expand host name for hops.
(tramp-dissect-hop-name, tramp-make-tramp-hop-name): New defuns.
(tramp-clear-passwd): Simplify.

* test/lisp/net/tramp-tests.el (tramp-test02-file-name-dissect)
(tramp-test02-file-name-dissect-simplified)
(tramp-test02-file-name-dissect-separate)
(tramp-test26-file-name-completion): Extend tests.

1 files changed, 8 insertions, 4 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 09f0362fed7..be6668ed42e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -172,7 +172,7 @@ the data.
 
 +++
 ** The Network Security Manager now allows more fine-grained control
-of what checks to run via the `network-security-protocol-checks'
+of what checks to run via the 'network-security-protocol-checks'
 variable.
 
 +++
@@ -356,7 +356,7 @@ shown in the currently selected window.
 ** Comint
 
 +++
-*** 'send-invisible' is now an obsolete alias for `comint-send-invisible'.
+*** 'send-invisible' is now an obsolete alias for 'comint-send-invisible'.
 Also, 'shell-strip-ctrl-m' is declared obsolete.
 
 +++
@@ -391,7 +391,7 @@ facilities to aid more casual SQL developers layout queries and
 complex expressions.
 
 *** 'sql-use-indent-support' (default t) enables SQL indention support.
-The `sql-indent' package from ELPA must be installed to get the
+The 'sql-indent' package from ELPA must be installed to get the
 indentation support in 'sql-mode' and 'sql-interactive-mode'.
 
 *** 'sql-mode-hook' and 'sql-interactive-mode-hook' changed.
@@ -420,7 +420,7 @@ This enables more efficient backends.  See the docstring of
 
 ** Package
 
-*** New function `package-get-version` lets packages query their own version.
+*** New function 'package-get-version' lets packages query their own version.
 Example use in auctex.el: (defconst auctex-version (package-get-version))
 
 *** New 'package-quickstart' feature.
@@ -747,6 +747,10 @@ are obsoleted in GVFS.
 *** The user option 'tramp-ignored-file-name-regexp' allows to disable
 Tramp for some look-alike remote file names.
 
++++
+*** For some connection methods, like "su" or "sudo", the host name in
+ad-hoc multi-hop file names must match the previous hop.
+
 ** Register
 ---
 *** The return value of method 'register-val-describe' includes the