[gimp-help] README, configure: `master` branch now targets GIMP 3.0.

[Jehan <jehanp src gnome org>]

commit eb0ad7be4af1464c2a5690c8339c89dacb3587ea
Author: Jehan <jehan girinstud io>
Date:   Tue Jun 15 18:39:52 2021 +0200

    README, configure: `master` branch now targets GIMP 3.0.
    
    As per the previous commit, the main branch has been forked into
    gimp-help-2-10 to continue working on GIMP 2.10 documentation.
    
    The main branch of this repository will now follow the main branch of
    the GIMP repository, hence can documents newest development features
    which will only be available when we will release GIMP 3.0.

 README       |  3 ++-
 configure.ac | 14 +++++++-------
 2 files changed, 9 insertions(+), 8 deletions(-)
---
diff --git a/README b/README
index 3eb7308ba..e8bbcdf7e 100644
--- a/README
+++ b/README
@@ -6,7 +6,8 @@ GIMP-Help is a help system designed for use with the internal GIMP help
 browser, external web browser and HTML renderers.
 Docbook is used to create a highly customizable documentation system.
 
-The current manual documents features for GIMP 2.10.
+The current manual documents features for the 2.99 development branch of
+GIMP which is a moving target for the future GIMP 3.0.
 
 Contents
 --------
diff --git a/configure.ac b/configure.ac
index 25282e69a..aea6f3e3e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5,7 +5,7 @@
 AC_PREREQ(2.54)
 
 m4_define([help_major_version], [2])
-m4_define([help_minor_version], [10])
+m4_define([help_minor_version], [99])
 m4_define([help_micro_version], [0])
 
 m4_define([help_version], [help_major_version.help_minor_version.help_micro_version])
@@ -303,20 +303,20 @@ AC_SUBST(STYLEBASE)
 
 AC_ARG_WITH(gimp,
             AS_HELP_STRING([--without-gimp],
-                           [skip check for gimp2, install into PREFIX]))
+                           [skip check for gimp3, install into PREFIX]))
 
 if test "x$with_gimp" != "xno"; then
   #  Note: AC_MSG_ERROR() must be bracket-quoted, or else errors result
-  PKG_CHECK_MODULES(GIMP, gimp-2.0, , [AC_MSG_ERROR([
-** Couldn't find a GIMP-2.0 installation. If you want to skip this check and
+  PKG_CHECK_MODULES(GIMP, gimp-3.0, , [AC_MSG_ERROR([
+** Couldn't find a GIMP-3.0 installation. If you want to skip this check and
 ** install the help files to the configured prefix, use the --without-gimp
 ** configure option. Note that GIMP will then only find the help files if it
 ** is installed in the same prefix. See the file 'INSTALL' for more help.])])
 
-  gimpdatadir=`$PKG_CONFIG --variable=gimpdatadir gimp-2.0`
+  gimpdatadir=`$PKG_CONFIG --variable=gimpdatadir gimp-3.0`
 else
-  gimpdatadir=`pkg-config --variable=gimpdatadir gimp-2.0` ||
-  gimpdatadir='$(datadir)/gimp/2.0'
+  gimpdatadir=`pkg-config --variable=gimpdatadir gimp-3.0` ||
+  gimpdatadir='$(datadir)/gimp/3.0'
 fi
 
 AC_SUBST(gimpdatadir)