[PATCH] aclocal: add m4 search path info to --help

Add a short summary to --help of the current paths that will be
searched.  Make sure to omit this from the man page when running
help2man since pre-inst-env specifically clears some and others
to the current build directory.

* bin/aclocal.in: Include m4 search paths in usage.
* doc/local.mk: Run help2man with AUTOMAKE_HELP2MAN=true.
---
 bin/aclocal.in | 20 +++++++++++++++++++-
 doc/local.mk   |  2 +-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/bin/aclocal.in b/bin/aclocal.in
index 857e85308cd3..36651c8c2882 100644
--- a/bin/aclocal.in
+++ b/bin/aclocal.in
@@ -1044,12 +1044,30 @@ Options:
                               third-party m4 files, then exit
       --verbose             don't be silent
       --version             print version number, then exit
-  -W, --warnings=CATEGORY   report the warnings falling in CATEGORY
+  -W, --warnings=CATEGORY   report the warnings falling in CATEGORY,
+                              defaults to $WARNINGS
+
 EOF
 
   print Automake::ChannelDefs::usage (), "\n";
 
+  # This output depends on the current environment, and when generating the man
+  # pages during Automake compilation, the environment is set to local values.
+  # So don't include it in the installed man page.
+  if (!$ENV{AUTOMAKE_HELP2MAN}) {
+    print <<"EOF";
+
+Current m4 search paths (in order):
+  -I dirs:                  @user_includes
+  --automake-acdir:         @automake_includes
+  \$ACLOCAL_AUTOMAKE_DIR:    $ENV{"ACLOCAL_AUTOMAKE_DIR"}
+  --system-acdir:           @system_includes
+  \$ACLOCAL_PATH:            $ENV{"ACLOCAL_PATH"}
+EOF
+  }
+
   print <<'EOF';
+
 Report bugs to <@PACKAGE_BUGREPORT@>.
 GNU Automake home page: <@PACKAGE_URL@>.
 General help using GNU software: <https://www.gnu.org/gethelp/>.
diff --git a/doc/local.mk b/doc/local.mk
index 06c78823a574..921e22e9ec54 100644
--- a/doc/local.mk
+++ b/doc/local.mk
@@ -37,7 +37,7 @@ EXTRA_DIST += %D%/help2man
 update_mans = \
   $(AM_V_GEN): \
     && $(MKDIR_P) %D% \
-    && ./pre-inst-env $(PERL) $(srcdir)/%D%/help2man --output=$@
+    && AUTOMAKE_HELP2MAN=true ./pre-inst-env $(PERL) $(srcdir)/%D%/help2man --output=$@
 
 %D%/aclocal.1 %D%/automake.1:
 	$(AM_V_GEN): \
-- 
2.34.1