Make configure less annoying

- Improve configure's notifications around the new features.
- Improve the info about man page generation and fetching.

INSTALL.md

@@ -13,6 +13,8 @@ You need to have a C compiler installed and optionally a C++ compiler in order
 to try to build some hardware-accelerated checksum routines.  Rsync also needs
 a modern awk, which might be provided via gawk or nawk on some OSes.
 
+## Autoconf & man pages
+
 If you're installing from the git repo (instead of a release tar file) you'll
 also need the GNU autotools (autoconf & automake) and your choice of 2 python3
 markdown libraries: cmarkgfm or commonmark (needed to generate the man pages).
@@ -22,6 +24,18 @@ build user (after installing python3's pip package):
 
 >     pip3 install --user commonmark
 
+You can test if you've got it fixed by running (from the src dir):
+
+>     ./md2man --test rsync-ssl.1.md
+
+Alternately, you can avoid generating the man pages by fetching the very latest
+versions (that match the latest git source) from the [generated-files][6] dir.
+One way to do that is to run:
+
+>     ./prepare-source fetchgen
+
+[6]: https://download.samba.org/pub/rsync/generated-files/
+
 ## ACL support
 
 To support copying ACL file information, make sure you have an acl

NEWS.md

@@ -88,6 +88,9 @@
 
  - Added a few more suffixes to the default skip-compress list.
 
+ - Improved configure's error handling to notify about several issues at once
+   instead of one by one (for the newest optional features).
+
 ### INTERNAL:
 
  - Use a simpler overflow check idiom in a few spots.

configure.ac

@@ -57,6 +57,11 @@ if test x"$ac_cv_prog_cc_stdc" = x"no"; then
 	AC_MSG_WARN([rsync requires an ANSI C compiler and you do not seem to have one])
 fi
 
+no_lib=''
+err_msg=''
+nl='
+'
+
 AC_ARG_ENABLE(profile,
 	AS_HELP_STRING([--enable-profile],[turn on CPU profiling]))
 if test x"$enable_profile" = x"yes"; then
@@ -88,8 +93,10 @@ if test x"$enable_md2man" != x"no"; then
     else
 	AC_MSG_RESULT(required)
 	if test x"$md2man_works" = x"no"; then
-	    AC_MSG_ERROR(You need python3 and the cmarkgfm OR commonmark python3 lib in order to build man pages.
-You can specify --disable-md2man if you want to skip building them.)
+	    err_msg="$err_msg$nl- You need python3 and either the cmarkgfm OR commonmark python3 lib in order"
+	    err_msg="$err_msg$nl  to build man pages based on the git source (man pages are included in the"
+	    err_msg="$err_msg$nl  official release tar files)."
+	    no_lib="$no_lib md2man"
 	fi
     fi
     MAKE_MAN=man
@@ -503,12 +510,12 @@ if test x"$enable_openssl" != x"no"; then
       AC_MSG_RESULT(yes)
       AC_SEARCH_LIBS(MD5_Init, crypto,
           [AC_DEFINE(USE_OPENSSL)],
-          [AC_MSG_ERROR(Failed to find MD5_Init function in openssl crypto lib.
-Use --disable-openssl to continue without openssl crypto lib support.)])
+          [err_msg="$err_msg$nl- Failed to find MD5_Init function in openssl crypto lib.";
+	   no_lib="$no_lib openssl"])
     else
         AC_MSG_RESULT(no)
-        AC_MSG_ERROR(Failed to find openssl/md4.h and openssl/md5.h for openssl crypto lib support.
-Use --disable-openssl to continue without it.)
+	err_msg="$err_msg$nl- Failed to find openssl/md4.h and openssl/md5.h for openssl crypto lib support."
+	no_lib="$no_lib openssl"
     fi
 else
     AC_MSG_RESULT(no)
@@ -524,12 +531,12 @@ if test x"$enable_xxhash" != x"no"; then
 	AC_MSG_RESULT(yes)
 	AC_SEARCH_LIBS(XXH64_createState, xxhash,
 	    [AC_DEFINE(SUPPORT_XXHASH)],
-	    [AC_MSG_ERROR(Failed to find XXH64_createState function in xxhash lib.
-Use --disable-xxhash to continue without xxhash checksums.)])
+	    [err_msg="$err_msg$nl- Failed to find XXH64_createState function in xxhash lib.";
+	     no_lib="$no_lib xxhash"])
     else
 	AC_MSG_RESULT(no)
-	AC_MSG_ERROR(Failed to find xxhash.h for xxhash checksum support.
-Use --disable-xxhash to continue without it.)
+	err_msg="$err_msg$nl- Failed to find xxhash.h for xxhash checksum support.";
+	no_lib="$no_lib xxhash"
     fi
 else
     AC_MSG_RESULT(no)
@@ -545,12 +552,12 @@ if test x"$enable_zstd" != x"no"; then
 	AC_MSG_RESULT(yes)
 	AC_SEARCH_LIBS(ZSTD_minCLevel, zstd,
 	    [AC_DEFINE(SUPPORT_ZSTD)],
-	    [AC_MSG_ERROR(Failed to find ZSTD_minCLevel function in zstd lib.
-Use --disable-zstd to continue without zstd compression.)])
+	    [err_msg="$err_msg$nl- Failed to find ZSTD_minCLevel function in zstd lib.";
+	     no_lib="$no_lib zstd"])
     else
 	AC_MSG_RESULT(no)
-	AC_MSG_ERROR(Failed to find zstd.h for zstd compression support.
-Use --disable-zstd to continue without it.)
+	err_msg="$err_msg$nl- Failed to find zstd.h for zstd compression support.";
+	no_lib="$no_lib zstd"
     fi
 else
     AC_MSG_RESULT(no)
@@ -566,17 +573,34 @@ if test x"$enable_lz4" != x"no"; then
 	AC_MSG_RESULT(yes)
 	AC_SEARCH_LIBS(LZ4_compress_default, lz4,
 	    [AC_DEFINE(SUPPORT_LZ4)],
-	    [AC_MSG_ERROR(Failed to find LZ4_compress_default function in lz4 lib.
-Use --disable-lz4 to continue without lz4 compression.)])
+	    [err_msg="$err_msg$nl- Failed to find LZ4_compress_default function in lz4 lib.";
+	     no_lib="$no_lib lz4"])
     else
 	AC_MSG_RESULT(no)
-	AC_MSG_ERROR(Failed to find lz4.h for lz4 compression support.
-Use --disable-lz4 to continue without it.)
+	err_msg="$err_msg$nl- Failed to find lz4.h for lz4 compression support."
+	no_lib="$no_lib lz4"
     fi
 else
     AC_MSG_RESULT(no)
 fi
 
+if test x"$no_lib" != x; then
+    echo ""
+    echo "Configure found the following issues:"
+    echo "$err_msg"
+    echo ""
+    echo "See the INSTALL file for hints on how to install the missing libraries and/or"
+    echo "how to generate (or fetch) man pages:"
+    echo "    https://github.com/WayneD/rsync/blob/master/INSTALL.md"
+    echo ""
+    echo "To disable one or more features, the relevant configure options are:"
+    for lib in $no_lib; do
+	echo "    --disable-$lib"
+    done
+    echo ""
+    AC_MSG_ERROR(Aborting configure run)
+fi
+
 AC_CACHE_CHECK([if makedev takes 3 args],rsync_cv_MAKEDEV_TAKES_3_ARGS,[
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <sys/types.h>