FYI: branch-1-5: backport --tag documentation

[Ralf Wildenhues]

I've backported those bits of the --tag documentation from HEAD that
apply to branch-1-5, see below.

Cheers,
Ralf

2007-01-27  Ralf Wildenhues  <address@hidden>

        * doc/libtool.texi (Invoking libtool): Document `--tag'.
        (Tags): New node, backported from HEAD.
        (Other languages): Adjust.
        * NEWS: Update.

Index: NEWS
===================================================================
RCS file: /cvsroot/libtool/libtool/NEWS,v
retrieving revision 1.109.2.50
diff -u -r1.109.2.50 NEWS
--- NEWS        21 Jan 2007 14:34:43 -0000      1.109.2.50
+++ NEWS        27 Jan 2007 17:26:00 -0000
@@ -14,6 +14,8 @@
 * Initial support for the Sun compiler suite on GNU/Linux.
 * Improved support for GNU/kFreeBSD and GNU/NetBSD.
 * Search paths with GCC on multilib systems like x86_64 have been fixed.
+* The libtool --tag argument which has been supported since version 1.5
+  is documented now.
 * Bug Fixes.
 
 New in 1.5.22: 2005-12-18; CVS version 1.5.21a, Libtool team:
Index: doc/libtool.texi
===================================================================
RCS file: /cvsroot/libtool/libtool/doc/libtool.texi,v
retrieving revision 1.134.2.18
diff -u -r1.134.2.18 libtool.texi
--- doc/libtool.texi    23 Jan 2007 23:49:27 -0000      1.134.2.18
+++ doc/libtool.texi    27 Jan 2007 17:26:02 -0000
@@ -172,7 +172,8 @@
 
 Using libtool with other languages
 
-* C++ libraries::
+* C++ libraries::               Writing libraries for C++
+* Tags::                        Tags
 
 Troubleshooting
 
@@ -1066,6 +1067,9 @@
 Display basic configuration options.  This provides a way for packages
 to determine whether shared or static libraries will be built.
 
address@hidden address@hidden
+Use configuration variables from tag @var{tag} (@pxref{Tags}).
+
 @item --preserve-dup-deps
 Do not remove duplicate dependencies in libraries.  When building packages
 with static libraries, the libraries may depend circularly on each other
@@ -3652,7 +3656,8 @@
 and what special considerations you need to make if you do not use C.
 
 @menu
-* C++ libraries::
+* C++ libraries::               Writing libraries for C++
+* Tags::                        Tags
 @end menu
 
 @node C++ libraries
@@ -3693,6 +3698,42 @@
 initialized.
 
 
address@hidden Tags
address@hidden Tags
address@hidden tag names
address@hidden language names
address@hidden inferring tags
+
+Libtool supports multiple languages through the use of tags.  Technically
+a tag corresponds to a set of configuration variables associated with a
+language.  These variables tell @command{libtool} how it should create
+objects and libraries for each language.
+
+Tags are defined at @command{configure}-time for each language activated
+in the package.  Here is the correspondence between language names and tags
+names.
+
address@hidden {Windows Resource} {Tag name}
address@hidden Language name    @tab Tag name
address@hidden C                @tab CC
address@hidden C++              @tab CXX
address@hidden Java             @tab GCJ
address@hidden Fortran 77       @tab F77
address@hidden Windows Resource @tab RC
address@hidden multitable
+
address@hidden tries to automatically infer which tag to use from
+the compiler command being used to compile or link.  If it can't infer
+a tag, then it defaults to the configuration for the @code{C} language.
+
+The tag can also be specified using @command{libtool}'s
address@hidden@var{tag}} option (@pxref{Invoking libtool}).  It is a good
+idea to do so in @file{Makefile} rules, because that will allow users to
+substitute the compiler without relying on @command{libtool} inference
+heuristics.  When no tag is specified, @command{libtool} will default
+to @code{CC}; this tag always exists.
+
+
 @node Troubleshooting
 @chapter Troubleshooting
 @cindex troubleshooting