emacs-27 b4937f6: Improve documentation of manually installing Lisp packages

[Eli Zaretskii]

branch: emacs-27
commit b4937f64cd97ff6bf93538987c014f8ea8ff9d34
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    Improve documentation of manually installing Lisp packages
    
    * doc/emacs/building.texi (Lisp Libraries): Describe how to
    manually load packages in the init file.  Mention the 'site-lisp'
    subdirectory of the default 'load-path'.
    
    * doc/emacs/package.texi (Packages): Describe manual installation
    of ELisp packages.  Suggested by Jean-Christophe Helary
    <address@hidden>.
---
 doc/emacs/building.texi | 32 ++++++++++++++++++++++++++++++++
 doc/emacs/package.texi  | 32 +++++++++++++++++++++++---------
 2 files changed, 55 insertions(+), 9 deletions(-)

diff --git a/doc/emacs/building.texi b/doc/emacs/building.texi
index e866eea..fa60ce2 100644
--- a/doc/emacs/building.texi
+++ b/doc/emacs/building.texi
@@ -1509,6 +1509,11 @@ putting a line like this in your init file (@pxref{Init 
File}):
 (add-to-list 'load-path "/path/to/my/lisp/library")
 @end example
 
+It is customary to put locally installed libraries in the
+@file{site-lisp} directory that is already in the default value of
+@code{load-path}, or in some subdirectory of @file{site-lisp}.  This
+way, you don't need to modify the default value of @code{load-path}.
+
 @cindex autoload
   Some commands are @dfn{autoloaded}; when you run them, Emacs
 automatically loads the associated library first.  For instance, the
@@ -1538,6 +1543,33 @@ compiled with XEmacs, a modified version of Emacs---they 
can cause
 Emacs to crash.  Set the variable @code{load-dangerous-libraries} to
 @code{t} if you want to try loading them.
 
+  Once you put your library in a directory where Emacs can find and
+load it, you may wish to make it available at startup.  This is useful
+when the library defines features that should be available
+automatically on demand, and manually loading the library is thus
+inconvenient.  In these cases, make sure the library will be loaded by
+adding suitable forms to your init file: either @code{load} or
+@code{require} (if you always need to load the library at startup), or
+@code{autoload} if you need Emacs to load the library when some
+command or function is invoked.  For example:
+
+@smalllisp
+@group
+ ;; Loads @file{my-shining-package.elc} unconditionally.
+ (require 'my-shining-package)
+@end group
+@group
+ ;; Will load @file{my-shining-package.elc} when @code{my-func} is invoked.
+ (autoload 'my-func "my-shining-package")
+@end group
+@end smalllisp
+
+  Note that installing a package using @code{package-install}
+(@pxref{Package Installation}) takes care of placing the package's
+Lisp files in a directory where Emacs will find it, and also writes
+the necessary initialization code into your init files, making the
+above manual customizations unnecessary.
+
 @node Lisp Eval
 @section Evaluating Emacs Lisp Expressions
 @cindex Emacs Lisp mode
diff --git a/doc/emacs/package.texi b/doc/emacs/package.texi
index 6bf4fc7..517d2b7 100644
--- a/doc/emacs/package.texi
+++ b/doc/emacs/package.texi
@@ -5,23 +5,37 @@
 @node Packages
 @chapter Emacs Lisp Packages
 @cindex Package
-@cindex Emacs Lisp package archive
 @cindex Package archive
 
-Emacs includes a facility that lets you easily download and install
-@dfn{packages} that implement additional features.  Each package is a
-separate Emacs Lisp program, sometimes including other components such
-as an Info manual.
+  Emacs is extended by implementing additional features in
+@dfn{packages}, which are Emacs Lisp libraries.  These could be
+written by you or provided by someone else.  If you want to install
+such a package so it is available in your future Emacs session, you
+need to compile it and put it in a directory where Emacs looks for
+Lisp libraries.  @xref{Lisp Libraries}, for more details about this
+manual installation method.  Many packages provide installation and
+usage instructions in the large commentary near the beginning of the
+Lisp file; you can use those instructions for installing and
+fine-tuning your use of the package.
 
-  @kbd{M-x list-packages} brings up a buffer named @file{*Packages*}
-with a list of all packages.  You can install or uninstall packages
-via this buffer.  @xref{Package Menu}.
+@cindex Emacs Lisp package archive
+  Packages can also be provided by @dfn{package archives}, which are
+large collections of Emacs Lisp packages.  Each package is a separate
+Emacs Lisp program, sometimes including other components such as an
+Info manual.  Emacs includes a facility that lets you easily download
+and install packages from such archives.  The rest of this chapter
+describes this facility.
+
+  To list the packages available for installation from package
+archives, type @w{@kbd{M-x list-packages @key{RET}}}.  It brings up a
+buffer named @file{*Packages*} with a list of all packages.  You can
+install or uninstall packages via this buffer.  @xref{Package Menu}.
 
   The command @kbd{C-h P} (@code{describe-package}) prompts for the
 name of a package, and displays a help buffer describing the
 attributes of the package and the features that it implements.
 
-  By default, Emacs downloads packages from a @dfn{package archive}
+  By default, Emacs downloads packages from a package archive
 maintained by the Emacs developers and hosted by the GNU project.
 Optionally, you can also download packages from archives maintained by
 third parties.  @xref{Package Installation}.