Deterministic build improvements

* configure.ac (BUILD_DETAILS): Rename from DETERMINISTIC_DUMP,
and negate its sense.  Use it via AC_SUBST, not AC_DEFINE,
and have its value be either empty or --no-build-details.
All uses changed.  Change option to --disable-build-details.
* doc/lispref/cmdargs.texi (Initial Options):
Document --no-build-details.
* doc/lispref/internals.texi (Building Emacs):
* etc/NEWS:
Document --disable-build-details.
* doc/lispref/intro.texi (Version Info): Say that
emacs-build-time can be nil.
* lisp/erc/erc-compat.el (erc-emacs-build-time):
Now nil if details are omitted.
* lisp/erc/erc.el (erc-cmd-SV):
* lisp/version.el (emacs-build-time):
Now nil if no build details.
(emacs-version):
Output build time only if build details.
* src/Makefile.in (BUILD_DETAILS): New macro.
(temacs, bootstrap-emacs): Use it.
* src/emacs.c (build_details): New var.
(standard_args, main): Support --no-build-details.
(Vdeterministic_dump): Remove; all uses replaced
by !build_details.
(syms_of_emacs): Set Vbuild_details to a boolean, not
to a Lisp_Object.
* src/lisp.h (build_details): New decl.
* src/sysdep.c (init_system_name): When !build_details,
set system-name to nil, not to "elided".

3 files changed, 19 insertions, 1 deletions

diff --git a/doc/emacs/cmdargs.texi b/doc/emacs/cmdargs.texi
index a842cb84abd..646c8da1bb8 100644
--- a/doc/emacs/cmdargs.texi
+++ b/doc/emacs/cmdargs.texi
@@ -283,6 +283,13 @@ which will invoke Emacs with @samp{--script} and supply the name of
 the script file as @var{file}.  Emacs Lisp then treats the @samp{#!}
 on this first line as a comment delimiter.
 
+@item --no-build-details
+@opindex --no-build-details
+@cindex build details
+@cindex deterministic build
+Omit details like system name and build time from the Emacs executable,
+so that builds are more deterministic.
+
 @item -q
 @opindex -q
 @itemx --no-init-file
diff --git a/doc/lispref/internals.texi b/doc/lispref/internals.texi
index 41064df5a28..fedef3d7f46 100644
--- a/doc/lispref/internals.texi
+++ b/doc/lispref/internals.texi
@@ -66,6 +66,16 @@ into the dumped Emacs.  If you port Emacs to a new operating system,
 and are not able to implement dumping, then Emacs must load
 @file{loadup.el} each time it starts.
 
+@cindex build details
+@cindex deterministic build
+@cindex @option{--disable-build-details} option to @command{configure}
+  By default the dumped @file{emacs} executable records details such
+as the build time and host name.  Use the
+@option{--disable-build-details} option of @command{configure} to
+suppress these details, so that building and installing Emacs twice
+from the same sources is more likely to result in identical copies of
+Emacs.
+
 @cindex @file{site-load.el}
   You can specify additional files to preload by writing a library named
 @file{site-load.el} that loads them.  You may need to rebuild Emacs
diff --git a/doc/lispref/intro.texi b/doc/lispref/intro.texi
index 0f42d4d8a7f..2f84aeee39e 100644
--- a/doc/lispref/intro.texi
+++ b/doc/lispref/intro.texi
@@ -494,7 +494,8 @@ giving a prefix argument makes @var{here} non-@code{nil}.
 @defvar emacs-build-time
 The value of this variable indicates the time at which Emacs was
 built.  It is a list of four integers, like the value of
-@code{current-time} (@pxref{Time of Day}).
+@code{current-time} (@pxref{Time of Day}), or is @code{nil}
+if the information is not available.
 
 @example
 @group