client: drop support for GNU readline

GNU readline switched to GPLv3+ in version 6.0, which is incompatible
with the chrony's GPLv2 license.

Drop support for the readline library. Only editline is supported now.

client.c

@@ -44,12 +44,7 @@
 #include "util.h"
 
 #ifdef FEAT_READLINE
-#ifdef USE_EDITLINE
 #include <editline/readline.h>
-#else
-#include <readline/readline.h>
-#include <readline/history.h>
-#endif
 #endif
 
 /* ================================================== */
@@ -1267,7 +1262,7 @@ give_help(void)
 }
 
 /* ================================================== */
-/* Tab-completion when editline/readline is available */
+/* Tab-completion when editline is available */
 
 #ifdef FEAT_READLINE
 

configure

@@ -108,11 +108,7 @@ for instance \`--prefix=$HOME'.
 
 For better control, use the options below.
   --disable-readline     Disable line editing support
-  --without-readline     Don't use GNU readline even if it is available
   --without-editline     Don't use editline even if it is available
-  --with-readline-includes=DIR Specify where readline include directory is
-  --with-readline-library=DIR Specify where readline lib directory is
-  --with-ncurses-library=DIR Specify where ncurses lib directory is
   --disable-sechash      Disable support for hashes other than MD5
   --without-nettle       Don't use nettle even if it is available
   --without-nss          Don't use NSS even if it is available
@@ -225,7 +221,6 @@ feat_cmdmon=1
 feat_ntp=1
 feat_refclock=1
 feat_readline=1
-try_readline=1
 try_editline=1
 feat_sechash=1
 try_nettle=1
@@ -241,9 +236,6 @@ try_clockctl=0
 feat_scfilter=0
 try_seccomp=-1
 priv_ops=""
-readline_lib=""
-readline_inc=""
-ncurses_lib=""
 feat_ipv6=1
 feat_phc=1
 try_phc=0
@@ -274,21 +266,9 @@ do
     --disable-readline )
       feat_readline=0
     ;;
-    --without-readline )
-      try_readline=0
-    ;;
     --without-editline )
       try_editline=0
     ;;
-    --with-readline-library=* )
-      readline_lib=-L`echo $option | sed -e 's/^.*=//;'`
-    ;;
-    --with-readline-includes=* )
-      readline_inc=-I`echo $option | sed -e 's/^.*=//;'`
-    ;;
-    --with-ncurses-library=* )
-      ncurses_lib=-L`echo $option | sed -e 's/^.*=//;'`
-    ;;
     --prefix=* | --install_prefix=* )
       SETPREFIX=`echo $option | sed -e 's/[^=]*=//;'`
     ;;
@@ -878,37 +858,11 @@ fi
 READLINE_LINK=""
 if [ $feat_readline = "1" ]; then
   if [ $try_editline = "1" ]; then
-    if test_code editline 'stdio.h editline/readline.h' \
-      "$readline_inc" "$readline_lib -ledit" \
+    if test_code editline 'stdio.h editline/readline.h' '' '-ledit' \
       'add_history(readline("prompt"));'
     then
       add_def FEAT_READLINE
-      add_def USE_EDITLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib -ledit"
-    fi
-  fi
-
-  if [ "x$READLINE_LINK" = "x" ] && [ $try_readline = "1" ]; then
-    if test_code readline 'stdio.h readline/readline.h readline/history.h' \
-      "$readline_inc" "$readline_lib -lreadline" \
-      'add_history(readline("prompt"));'
-    then
-      add_def FEAT_READLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib -lreadline"
-    fi
-  fi
-
-  if [ "x$READLINE_LINK" = "x" ] && [ $try_readline = "1" ]; then
-    if test_code 'readline with -lncurses' \
-      'stdio.h readline/readline.h readline/history.h' \
-      "$readline_inc" "$readline_lib $ncurses_lib -lreadline -lncurses" \
-      'add_history(readline("prompt"));'
-    then
-      add_def FEAT_READLINE
-      MYCPPFLAGS="$MYCPPFLAGS $readline_inc"
-      READLINE_LINK="$readline_lib $ncurses_lib -lreadline -lncurses"
+      READLINE_LINK="-ledit"
     fi
   fi
 

doc/installation.adoc

@@ -100,7 +100,7 @@ than MD5, which can be used for NTP authentication with a symmetric key. If you
 don't want to enable the support, specify the `--disable-sechash` flag to
 `configure`.
 
-If development files for the editline or readline library are available,
+If development files for the editline library are available,
 `chronyc` will be built with line editing support. If you don't want this,
 specify the `--disable-readline` flag to `configure`.
 
@@ -170,43 +170,6 @@ https://github.com/seccomp/libseccomp[libseccomp] library and the
 the kernel attack surface and possibly prevent kernel exploits from `chronyd`
 if it is compromised.
 
-== Support for line editing libraries
-
-`chronyc` can be built with support for line editing, this allows you to use
-the cursor keys to replay and edit old commands. Two libraries are supported
-which provide such functionality, editline and GNU readline.
-
-Please note that readline since version 6.0 is licensed under GPLv3+ which is
-incompatible with chrony's license GPLv2. You should use editline instead if
-you don't want to use older readline versions.
-
-The `configure` script will automatically enable the line editing support if
-one of the supported libraries is available. If they are both available, the
-editline library will be used.
-
-If you don't want to use it (in which case `chronyc` will use a minimal command
-line interface), invoke `configure` like this:
-
-----
-./configure --disable-readline other-options...
-----
-
-If you have editline, readline or ncurses installed in locations that aren't
-normally searched by the compiler and linker, you need to use extra options:
-
-`--with-readline-includes=directory_name`::
-  This defines the name of the directory above the one where `readline.h` is.
-  `readline.h` is assumed to be in `editline` or `readline` subdirectory of the
-  named directory.
-
-`--with-readline-library=directory_name`::
-  This defines the directory containing the `libedit.a` or `libedit.so` file,
-  or `libreadline.a` or `libreadline.so` file.
-
-`--with-ncurses-library=directory_name`::
-  This defines the directory containing the `libncurses.a` or `libncurses.so`
-  file.
-
 == Extra options for package builders
 
 The `configure` and `make` procedures have some extra options that may be