Re: [PATCH] describe --local-dir option in documentation

[Ben Pfaff]

Bruno Haible <address@hidden> writes:

> Thanks for the work on this. Looks quite good, nearly ready to commit.
>
> Just three small remarks:
>
>> +``foobar'' needs a modified version of, say, @file{stdint_.h}, it
>
> Nowadays this file is called @file{stdint.in.h}.

Thanks, I've fixed that now.

>> ... or it has to use the
>> address@hidden option and provide the modified @code{stdint}
>> +module in a different directory and use libtool convenience libraries.
>
> I don't understand the part "and use libtool convenience libraries". The
> user can provide a modified module, and gnulib-tool will use the
> modified module just like it would use the original gnulib module. There
> is no need to create a .a library that includes another .a library.
> Additionally, the 'stdint' module does not provide a .o file, making
> this sentence even more confusing. [Yes I know it was me who wrote this
> sentence 4 years ago ;-)]

I didn't understand that part either, but I assumed that you did ;-)
I fixed this by just deleting the "and use libtool convenience
libraries" part of the sentence.

>> address@hidden
>> +You can also add unstructured amounts of code to the library, by grouping
>> +the non-Gnulib files of the library in a single kitchen-sink ``module.''
>
> Here one could add a remark that this kind of kitchen-sink module is not
> needed when you use the gnulib-tool option @samp{--makefile-name}.

I haven't used that option and don't see any documentation
(besides --help), so I'm not certain how it helps.  I could
guess, but I decided to just add this to the bullet: "(This kind
of kitchen-sink module is not needed when you use the
@command{gnulib-tool} option @samp{--makefile-name}.)"  If you
want to edit it to explain better, that is probably a good idea.

> You are then welcome to commit and push this. Many thanks!

And thank you for your helpful comments.

I pushed it out, as follows:

--8<--------------------------cut here-------------------------->8--

>From 47e899ad11a04647942b39dd501bfc2381e9b2f0 Mon Sep 17 00:00:00 2001
From: Ben Pfaff <address@hidden>
Date: Wed, 9 Jun 2010 20:53:13 -0700
Subject: [PATCH] Add "Extending Gnulib" chapter to manual.

* doc/gnulib.texi (Writing Modules): Add cross-reference to new chapter.
(Extending Gnulib): New chapter.
* doc/gnulib-intro.texi (Openness): Add cross-reference to new chapter.
---
 ChangeLog             |   10 ++++++
 doc/gnulib-intro.texi |    4 +-
 doc/gnulib.texi       |   83 +++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 93 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 57d9e2c..71803c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2010-06-09  Ben Pfaff  <address@hidden>
+            Bruno Haible  <address@hidden>
+
+       Add "Extending Gnulib" chapter to manual.
+       * doc/gnulib.texi (Writing Modules): Add cross-reference to new
+       chapter.
+       (Extending Gnulib): New chapter.
+       * doc/gnulib-intro.texi (Openness): Add cross-reference to new
+       chapter.
+
 2010-06-09  Bruno Haible  <address@hidden>
 
        Avoid relocwrapper link errors due to gnulib replacement functions.
diff --git a/doc/gnulib-intro.texi b/doc/gnulib-intro.texi
index 4cb86b8..52191ec 100644
--- a/doc/gnulib-intro.texi
+++ b/doc/gnulib-intro.texi
@@ -346,5 +346,5 @@ locally add modules that are treated like Gnulib modules by
 @code{gnulib-tool}.
 @end enumerate
 
-This is achieved by the @samp{--local-dir} option of @code{gnulib-tool}.
-
+This is achieved by the @samp{--local-dir} option of @code{gnulib-tool}
+(@pxref{Extending Gnulib}).
diff --git a/doc/gnulib.texi b/doc/gnulib.texi
index 4cbc9e7..a1f5446 100644
--- a/doc/gnulib.texi
+++ b/doc/gnulib.texi
@@ -54,6 +54,7 @@ Documentation License''.
 * Introduction::
 * Invoking gnulib-tool::
 * Writing modules::
+* Extending Gnulib::
 * Miscellaneous Notes::
 * POSIX Substitutes Library::       Building as a separate substitutes library.
 * Header File Substitutes::         Overriding system headers.
@@ -117,8 +118,8 @@ Resources:
 @node Writing modules
 @chapter Writing modules
 
-This chapter explains how to write modules of your own, either for your own
-package (to be used with gnulib-tool's @samp{--local-dir} option), or for
+This chapter explains how to write modules of your own, either to
+extend Gnulib for your own package (@pxref{Extending Gnulib}), or for
 inclusion in gnulib proper.
 
 The guidelines in this chapter do not necessarily need to be followed for
@@ -608,6 +609,84 @@ before every release.
 @end enumerate
 
 
address@hidden Extending Gnulib
address@hidden Extending Gnulib
+
+Gnulib modules are intended to be suitable for widespread use.  Most
+problems with Gnulib can and should be fixed in a generic way, so that
+all of Gnulib's users can benefit from the change.  But occasionally a
+problem arises that is difficult or undesirable to fix generically, or
+a project that uses Gnulib may need to work around an issue before the
+Gnulib maintainers commit a final fix.  Maintainers may also want to
+add their own pools of modules to projects as Gnulib ``staging
+areas.''
+
+The obvious way to make local changes to Gnulib modules is to use
address@hidden to check out pristine modules, then to modify
+the results in-place.  This works well enough for short-lived
+experiments.  It is harder to keep modified versions of Gnulib modules
+for a long time, even though Git (or another distributed version
+control systems) can help out a lot with this during the development
+process.
+
+Git, however, doesn't address the distribution issue.  When a package
+``foobar'' needs a modified version of, say, @file{stdint.in.h}, it
+either has to put a comment into @file{foobar/autogen.sh} saying
+``Attention! This doesn't work with a pristine Gnulib, you need this
+and that patch after checking out Gnulib,'' or it has to use the
address@hidden option and provide the modified @code{stdint}
+module in a different directory.
+
+The @option{--local-dir} option to @command{gnulib-tool} solves this
+problem.  It allows the package to override or augment Gnulib.  This
+means:
+
address@hidden @bullet
address@hidden
+You can store files that are to override Gnulib files or modules.
+
address@hidden
+You can store context diffs to be applied to Gnulib files.
+
address@hidden
+You can add modules of your own, that are not (yet) in Gnulib.
+
address@hidden
+You can also add unstructured amounts of code to the library, by
+grouping the non-Gnulib files of the library in a single kitchen-sink
+``module.''  (This kind of kitchen-sink module is not needed when you
+use the @command{gnulib-tool} option @samp{--makefile-name}.)
address@hidden itemize
+
+In a release tarball, you can distribute the contents of this
address@hidden directory that will be combinable with newer
+versions of Gnulib, barring incompatible changes to Gnulib.
+
+If the @address@hidden option is specified, then
address@hidden looks in @address@hidden whenever it
+reads a file from the Gnulib directory.  Suppose @command{gnulib-tool}
+is looking for @var{file}.  Then:
+
address@hidden @bullet
address@hidden
+If @address@hidden/@var{file}} exists, then @samp{gnulib-tool} uses
+it instead of the file included in Gnulib.
+
address@hidden
+Otherwise, if @address@hidden/@var{file}.diff} exists, then
address@hidden uses the file from Gnulib after applying the diff
+using the @command{patch} program.
+
address@hidden
+Otherwise, @command{gnulib-tool} uses the file included in Gnulib.
address@hidden itemize
+
+Please make wise use of this option.  It also allows you to easily
+hold back modifications you make to Gnulib macros in cases it may be
+better to share them.
+
+
+
 @node Miscellaneous Notes
 @chapter Miscellaneous Notes
 
-- 
1.7.1


-- 
"Sanity is not statistical."
--George Orwell