Generate date for the man page

* Makefile.am (dist-hook): Add .strace.1.in.date generation.
* strace.spec.in (%setup): Likewise.
* configure.ac (manpage_date): New m4 define.
(MANPAGE_DATE): New define/subst.
* strace.1 (.TH): Add manpage date and strace's version.

Makefile.am

@@ -884,6 +884,7 @@ sen.h: $(patsubst %,$(srcdir)/%,$(syscallent_files))
 dist-hook:
 	$(AM_V_GEN)echo $(VERSION) > $(distdir)/.tarball-version
 	${AM_V_GEN}echo $(COPYRIGHT_YEAR) > $(distdir)/.year
+	${AM_V_GEN}echo $(MANPAGE_DATE) > $(distdir)/.strace.1.in.date
 
 today = $(shell date +%Y-%m-%d)
 version_regexp = $(subst .,\.,$(VERSION))

configure.ac

@@ -37,6 +37,7 @@ AC_INIT([strace],
 	[strace],
 	[https://strace.io])
 m4_define([copyright_year], m4_esyscmd([./copyright-year-gen .year]))
+m4_define([manpage_date], m4_esyscmd([./file-date-gen strace.1.in]))
 AC_COPYRIGHT([Copyright (c) 1999-]copyright_year[ The strace developers.])
 AC_CONFIG_SRCDIR([strace.c])
 AC_CONFIG_AUX_DIR([.])
@@ -63,6 +64,9 @@ AX_CODE_COVERAGE
 AC_DEFINE([COPYRIGHT_YEAR], "[copyright_year]", [Current copyright year.])
 AC_SUBST([COPYRIGHT_YEAR], [copyright_year])
 
+AC_DEFINE([MANPAGE_DATE], "[manpage_date]", [Date])
+AC_SUBST([MANPAGE_DATE], [manpage_date])
+
 AC_MSG_CHECKING([for supported architecture])
 arch_m32=
 arch_mx32=

strace.1.in

@@ -51,7 +51,7 @@
 .  el \
 .    BR "\\$1"
 ..
-.TH STRACE 1
+.TH STRACE 1 "@MANPAGE_DATE@" "strace @VERSION@"
 .SH NAME
 strace \- trace system calls and signals
 .SH SYNOPSIS

strace.spec.in

@@ -49,6 +49,7 @@ The `strace' program in the `strace' package is for 32-bit processes.
 %setup -q
 echo -n %version-%release > .tarball-version
 echo -n @COPYRIGHT_YEAR@ > .year
+echo -n @MANPAGE_DATE@ > .strace.1.in.date
 
 %build
 echo 'BEGIN OF BUILD ENVIRONMENT INFORMATION'