Add common header with serial to all *.m4 files

The serial number can be useful for aclocal to choose
the newest one when it encounters the same foo.m4 file
in more than one place.

31 files changed, 186 insertions, 0 deletions

diff --git a/libgphoto2_port/gphoto-m4/gp-asm-symver-ifelse.m4 b/libgphoto2_port/gphoto-m4/gp-asm-symver-ifelse.m4
index 33174f8f5..4c2ffa805 100644
--- a/libgphoto2_port/gphoto-m4/gp-asm-symver-ifelse.m4
+++ b/libgphoto2_port/gphoto-m4/gp-asm-symver-ifelse.m4
@@ -1,3 +1,9 @@
+# gp-asm-symver-ifelse.m4 - check for asm .symver              -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl GP_ASM_SYMVER_IFELSE([ACTION-IF-TRUE], [ACTION-IF-FALSE])
 dnl ####################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-asm-symver-support.m4 b/libgphoto2_port/gphoto-m4/gp-asm-symver-support.m4
index 1b1826474..96cfe8d28 100644
--- a/libgphoto2_port/gphoto-m4/gp-asm-symver-support.m4
+++ b/libgphoto2_port/gphoto-m4/gp-asm-symver-support.m4
@@ -1,3 +1,9 @@
+# gp-asm-symver-support.m4 - check for asm .symver; def macros -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl If compiler supports asm .symver, define HAVE_ASM_SYMVER C preprocessor macro and Automake conditional
 dnl ####################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-byteorder.m4 b/libgphoto2_port/gphoto-m4/gp-byteorder.m4
index f80c67f66..d7810d68b 100644
--- a/libgphoto2_port/gphoto-m4/gp-byteorder.m4
+++ b/libgphoto2_port/gphoto-m4/gp-byteorder.m4
@@ -1,3 +1,9 @@
+# gp-byteorder.m4 - check byteorder and provide functions      -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl AC_NEED_BYTEORDER_H ( HEADER-TO-GENERATE )
 dnl Originally written by Dan Fandrich <dan@coneharvesters.com>
 dnl My contribution is hereby placed into the public domain.
diff --git a/libgphoto2_port/gphoto-m4/gp-camlibs.m4 b/libgphoto2_port/gphoto-m4/gp-camlibs.m4
index f61a9777f..9deaee3e3 100644
--- a/libgphoto2_port/gphoto-m4/gp-camlibs.m4
+++ b/libgphoto2_port/gphoto-m4/gp-camlibs.m4
@@ -1,3 +1,9 @@
+# gp-camlibs.m4 - define camlibs and camlib infrastructure     -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl
 dnl GP_CAMLIB & Co.
diff --git a/libgphoto2_port/gphoto-m4/gp-check-doxygen.m4 b/libgphoto2_port/gphoto-m4/gp-check-doxygen.m4
index 044fcb02c..fe4075d06 100644
--- a/libgphoto2_port/gphoto-m4/gp-check-doxygen.m4
+++ b/libgphoto2_port/gphoto-m4/gp-check-doxygen.m4
@@ -1,3 +1,9 @@
+# gp-check-doxygen.m4 - check for doxygen tool                 -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl doxygen related stuff
 dnl look for tools
diff --git a/libgphoto2_port/gphoto-m4/gp-check-library.m4 b/libgphoto2_port/gphoto-m4/gp-check-library.m4
index ee9ef004b..209e1ce89 100644
--- a/libgphoto2_port/gphoto-m4/gp-check-library.m4
+++ b/libgphoto2_port/gphoto-m4/gp-check-library.m4
@@ -1,3 +1,9 @@
+# gp-check-library.m4 - generic library check                  -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl @synopsis GP_CHECK_LIBRARY([VARNAMEPART],[libname],[VERSION-REQUIREMENT],
 dnl                            [headername],[functionname],
 dnl                            [ACTION-IF-FOUND],[ACTION-IF-NOT-FOUND],
diff --git a/libgphoto2_port/gphoto-m4/gp-check-popt.m4 b/libgphoto2_port/gphoto-m4/gp-check-popt.m4
index 7b8b6aa8f..a8b3718f2 100644
--- a/libgphoto2_port/gphoto-m4/gp-check-popt.m4
+++ b/libgphoto2_port/gphoto-m4/gp-check-popt.m4
@@ -1,3 +1,9 @@
+# gp-check-popt.m4 - check for libpopt                         -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl @synopsis GP_CHECK_POPT(FLAG)
 dnl
 dnl Check whether libpopt is available.
diff --git a/libgphoto2_port/gphoto-m4/gp-check-shell-environment.m4 b/libgphoto2_port/gphoto-m4/gp-check-shell-environment.m4
index 3a84c5e06..1a4e7d4eb 100644
--- a/libgphoto2_port/gphoto-m4/gp-check-shell-environment.m4
+++ b/libgphoto2_port/gphoto-m4/gp-check-shell-environment.m4
@@ -1,3 +1,9 @@
+# gp-check-shell-environment.m4 - check for sane shell environ -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl @synopsis GP_CHECK_SHELL_ENVIRONMENT([SHOW-LOCALE-VARS])
 dnl 
 dnl Check that the shell environment is sane.
diff --git a/libgphoto2_port/gphoto-m4/gp-config-msg.m4 b/libgphoto2_port/gphoto-m4/gp-config-msg.m4
index cc1935182..c81d88af4 100644
--- a/libgphoto2_port/gphoto-m4/gp-config-msg.m4
+++ b/libgphoto2_port/gphoto-m4/gp-config-msg.m4
@@ -1,3 +1,9 @@
+# gp-config-msg.m4 - define config message summary             -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl
 dnl GP_CONFIG_INIT
 dnl      use default LHS width (called implicitly if not called explicitly)
diff --git a/libgphoto2_port/gphoto-m4/gp-documentation.m4 b/libgphoto2_port/gphoto-m4/gp-documentation.m4
index 0efb3f4f5..45f44b344 100644
--- a/libgphoto2_port/gphoto-m4/gp-documentation.m4
+++ b/libgphoto2_port/gphoto-m4/gp-documentation.m4
@@ -1,3 +1,9 @@
+# gp-documentation.m4 - whether to build our gtk-doc docs      -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl check whether to build docs and where to:
 dnl
diff --git a/libgphoto2_port/gphoto-m4/gp-driverdir.m4 b/libgphoto2_port/gphoto-m4/gp-driverdir.m4
index 52895c085..930e2faed 100644
--- a/libgphoto2_port/gphoto-m4/gp-driverdir.m4
+++ b/libgphoto2_port/gphoto-m4/gp-driverdir.m4
@@ -1,3 +1,9 @@
+# gp-driverdir.m4 - define install dirs for camlibs and iolibs -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ###################################################################
 dnl Driver directory (camlibdir or iolibdir)
 dnl ###################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-gettext-setup.m4 b/libgphoto2_port/gphoto-m4/gp-gettext-setup.m4
index 30531c3c2..2626384c6 100644
--- a/libgphoto2_port/gphoto-m4/gp-gettext-setup.m4
+++ b/libgphoto2_port/gphoto-m4/gp-gettext-setup.m4
@@ -1,3 +1,9 @@
+# gp-gettext-setup.m4 - set up gettext with some checks        -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl GP_GETTEXT_SETUP(...)
 dnl    Gettext setup with e.g. consistency checks for value of DOMAIN.
diff --git a/libgphoto2_port/gphoto-m4/gp-internal-docs.m4 b/libgphoto2_port/gphoto-m4/gp-internal-docs.m4
index 01c4768db..4b40eb031 100644
--- a/libgphoto2_port/gphoto-m4/gp-internal-docs.m4
+++ b/libgphoto2_port/gphoto-m4/gp-internal-docs.m4
@@ -1,3 +1,9 @@
+# gp-internal-docs.m4 - whether include internals in docs      -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl
 dnl
 dnl
diff --git a/libgphoto2_port/gphoto-m4/gp-libjpeg.m4 b/libgphoto2_port/gphoto-m4/gp-libjpeg.m4
index a60a15f03..774de024a 100644
--- a/libgphoto2_port/gphoto-m4/gp-libjpeg.m4
+++ b/libgphoto2_port/gphoto-m4/gp-libjpeg.m4
@@ -1,3 +1,9 @@
+# gp-libjpeg.m4 - check for libjpeg                            -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl GP_LIBJPEG
 dnl ####################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-libltdl.m4 b/libgphoto2_port/gphoto-m4/gp-libltdl.m4
index db931dcd3..9680318d8 100644
--- a/libgphoto2_port/gphoto-m4/gp-libltdl.m4
+++ b/libgphoto2_port/gphoto-m4/gp-libltdl.m4
@@ -1,3 +1,9 @@
+# gp-libltdl.m4 - check for libltdl (from libtool)             -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl Written by Hans Ulrich Niedermann
 dnl LDFLAGS vs LIBS fix by Dan Nicholson
 dnl
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-docbook-xml.m4 b/libgphoto2_port/gphoto-m4/gp-manual-docbook-xml.m4
index 4c2be1bc4..0522a4830 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-docbook-xml.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-docbook-xml.m4
@@ -1,3 +1,9 @@
+# gp-manual-docbook-xml.m4 - look for xmlto and related things -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ------------------------------------------------------------------------
 dnl try to find xmlto (required for generation of man pages and html docs)
 dnl ------------------------------------------------------------------------
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-documentation.m4 b/libgphoto2_port/gphoto-m4/gp-manual-documentation.m4
index d73649eaa..f4aadc596 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-documentation.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-documentation.m4
@@ -1,3 +1,9 @@
+# gp-manual-documentation.m4 - define doc dirs and doc formats -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl
 dnl check where to install documentation
 dnl
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-fig2dev.m4 b/libgphoto2_port/gphoto-m4/gp-manual-fig2dev.m4
index 0eee53360..3521ae4c1 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-fig2dev.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-fig2dev.m4
@@ -1,3 +1,9 @@
+# gp-manual-fig2dev.m4 - look for fig2dev tool and check it    -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ---------------------------------------------------------------------------
 dnl fig2dev: This program is needed for processing images. If not found,
 dnl          documentation can still be built, but without figures.
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-graphviz.m4 b/libgphoto2_port/gphoto-m4/gp-manual-graphviz.m4
index e901ac231..3b6f87d23 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-graphviz.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-graphviz.m4
@@ -1,3 +1,9 @@
+# gp-manual-graphviz.m4 - look for graphviz dot tool; check it -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ---------------------------------------------------------------------------
 dnl dot: This program is needed for processing images. If not found,
 dnl          documentation can still be built, but without figures.
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-gtk-doc.m4 b/libgphoto2_port/gphoto-m4/gp-manual-gtk-doc.m4
index b07213b86..6e16c9f68 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-gtk-doc.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-gtk-doc.m4
@@ -1,3 +1,9 @@
+# gp-manual-gtk-doc.m4 - whether to build docs using gtk-doc   -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ---------------------------------------------------------------------------
 dnl gtk-doc: We use gtk-doc for building our documentation. However, we
 dnl          require the user to explicitly request the build.
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-pstoimg.m4 b/libgphoto2_port/gphoto-m4/gp-manual-pstoimg.m4
index cef82d6e5..7616ce882 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-pstoimg.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-pstoimg.m4
@@ -1,3 +1,9 @@
+# gp-manual-pstoimg.m4 - look for pstoimg tool                 -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ---------------------------------------------------------------------------
 dnl pstoimg: This program is needed for processing images. If not found,
 dnl          documentation can still be built, but without figures.
diff --git a/libgphoto2_port/gphoto-m4/gp-manual-w3m.m4 b/libgphoto2_port/gphoto-m4/gp-manual-w3m.m4
index 4006cba53..fc77352b7 100644
--- a/libgphoto2_port/gphoto-m4/gp-manual-w3m.m4
+++ b/libgphoto2_port/gphoto-m4/gp-manual-w3m.m4
@@ -1,3 +1,9 @@
+# gp-manual-w3m.m4 - look for w3m tool for html>txt conversion -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ---------------------------------------------------------------------------
 dnl w3m: This program is needed for converting HTML to text.
 dnl ---------------------------------------------------------------------------
diff --git a/libgphoto2_port/gphoto-m4/gp-packaging.m4 b/libgphoto2_port/gphoto-m4/gp-packaging.m4
index 9221d0886..9dcbcdc6b 100644
--- a/libgphoto2_port/gphoto-m4/gp-packaging.m4
+++ b/libgphoto2_port/gphoto-m4/gp-packaging.m4
@@ -1,3 +1,9 @@
+# gp-packaging.m4 - help with packaging libgphoto2 for distros -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 AC_DEFUN([GPKG_CHECK_LINUX],
 [
 	# effective_target has to be determined in advance
diff --git a/libgphoto2_port/gphoto-m4/gp-pedantic-compiler-flags.m4 b/libgphoto2_port/gphoto-m4/gp-pedantic-compiler-flags.m4
index 1b690428c..90c785863 100644
--- a/libgphoto2_port/gphoto-m4/gp-pedantic-compiler-flags.m4
+++ b/libgphoto2_port/gphoto-m4/gp-pedantic-compiler-flags.m4
@@ -1,3 +1,9 @@
+# gp-pedantic-compiler-flags.m4 - have compiler warn a LOT     -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl GP_PEDANTIC_COMPILER_FLAGS & Co.
 dnl ####################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-progs.m4 b/libgphoto2_port/gphoto-m4/gp-progs.m4
index beae29b3e..2f7dcdbf7 100644
--- a/libgphoto2_port/gphoto-m4/gp-progs.m4
+++ b/libgphoto2_port/gphoto-m4/gp-progs.m4
@@ -1,3 +1,9 @@
+# gp-progs.m4 - look for certain well-known tools              -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl Find a number of common programs, but allow setting a variable
 dnl to use a specific implementation.
diff --git a/libgphoto2_port/gphoto-m4/gp-references.m4 b/libgphoto2_port/gphoto-m4/gp-references.m4
index 7f00d06b4..797cf686a 100644
--- a/libgphoto2_port/gphoto-m4/gp-references.m4
+++ b/libgphoto2_port/gphoto-m4/gp-references.m4
@@ -1,3 +1,9 @@
+# gp-references.m4 - define some URLs as constants             -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl
 dnl Define external references
 dnl
diff --git a/libgphoto2_port/gphoto-m4/gp-set.m4 b/libgphoto2_port/gphoto-m4/gp-set.m4
index f9a061ec2..66056c2b2 100644
--- a/libgphoto2_port/gphoto-m4/gp-set.m4
+++ b/libgphoto2_port/gphoto-m4/gp-set.m4
@@ -1,3 +1,9 @@
+# gp-set.m4 - implement configure time set arithmetic          -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ######################################################################
 dnl Set operations using shell
 dnl ######################################################################
diff --git a/libgphoto2_port/gphoto-m4/gp-sleep.m4 b/libgphoto2_port/gphoto-m4/gp-sleep.m4
index 2c4014892..969a19277 100644
--- a/libgphoto2_port/gphoto-m4/gp-sleep.m4
+++ b/libgphoto2_port/gphoto-m4/gp-sleep.m4
@@ -1,3 +1,9 @@
+# gp-sleep.m4 - look for the sleep(1) tool                     -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl ####################################################################
 dnl GP_SLEEP(delay_in_whole_seconds)
 dnl   If the SLEEP variable is set to "no" or empty or is unset,
diff --git a/libgphoto2_port/gphoto-m4/gp-subpackage.m4 b/libgphoto2_port/gphoto-m4/gp-subpackage.m4
index d0978f997..87d1f5dfd 100644
--- a/libgphoto2_port/gphoto-m4/gp-subpackage.m4
+++ b/libgphoto2_port/gphoto-m4/gp-subpackage.m4
@@ -1,3 +1,9 @@
+# gp-subpackage.m4 - whether to enable a subpackage            -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 AC_DEFUN([GP_SUBPACKAGE],
 [
 AC_ARG_VAR([enable_subpackage_][$1], [enable subpackage ][$1][ (true or false)])
diff --git a/libgphoto2_port/gphoto-m4/gp-udev.m4 b/libgphoto2_port/gphoto-m4/gp-udev.m4
index c6b70873c..9dfc3d7a8 100644
--- a/libgphoto2_port/gphoto-m4/gp-udev.m4
+++ b/libgphoto2_port/gphoto-m4/gp-udev.m4
@@ -1,3 +1,9 @@
+# gp-udev.m4 - check for udev                                  -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl Determines whether UDEV code should be compiled.
 dnl $1 contains shell code that returns 0 if all other prerequisites (like
 dnl libusb) are available.
diff --git a/libgphoto2_port/gphoto-m4/gp-va-copy.m4 b/libgphoto2_port/gphoto-m4/gp-va-copy.m4
index 8b1ac85c7..0ae17f39a 100644
--- a/libgphoto2_port/gphoto-m4/gp-va-copy.m4
+++ b/libgphoto2_port/gphoto-m4/gp-va-copy.m4
@@ -1,3 +1,9 @@
+# gp-va-copy.m4 - check for va_copy                            -*- Autoconf -*-
+# serial 13
+dnl | Increment the above serial number every time you edit this file.
+dnl | When it finds multiple m4 files with the same name,
+dnl | aclocal will use the one with the highest serial.
+dnl
 dnl @synopsis GP_VA_COPY
 dnl
 dnl Checks whether one of these compiles and links: