fakedate: simplify logic

Using -ef to check for the same file is nicer than relying on a magic
symlink-to-fakedate.

Notice that -ef isn't stricly posix (but supported by bash/dash/zsh), so
I've changed the shebang to /bin/bash.

While we are at it, restructure the logic to do a single exec at the end
instead of handling the epoch/!epoch cases differently for simplicity.

With that out of the way we can directly install it as $HOST/usr/bin/date
instead of the fakedate / date symlink.

[Peter: drop IFS=: change]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/fakedate/fakedate

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # vim: set sw=4 expandtab:
 #
 # This program is free software; you can redistribute it and/or modify
@@ -18,18 +18,12 @@
 # Copyright (C) 2016 Jérôme Pouiller <jezz@sysmic.org>
 #
 
-# Sanity check
-if ! readlink -f "$0" | grep -q fakedate; then
-    echo "fakedate: Please name this script \`fakedate'"
-    exit 1
-fi
-
 DATE_BIN=false
 # Do not call `date' directly since it will produce an infinite recursion.
 # Instead, find path of true `date' binary.
 for P in `echo $PATH | tr ':' ' '`; do
     if [ -x "$P/date" ]; then
-        if readlink -f "$P/date" | grep -qv fakedate; then
+        if ! [ "$P/date" -ef "$0" ]; then
             DATE_BIN="$P/date"
             break;
         fi
@@ -50,8 +44,8 @@ if [ -n "$SOURCE_DATE_EPOCH" ]; then
     done
     if [ $FORCE_EPOCH -eq 1 ]; then
         echo "date: Warning: using \$SOURCE_DATE_EPOCH instead of true time" >&2
-        exec $DATE_BIN -d "@$SOURCE_DATE_EPOCH" "$@"
+        ARGS="-d @$SOURCE_DATE_EPOCH"
     fi
 fi
 
-exec $DATE_BIN "$@"
+exec $DATE_BIN $ARGS "$@"

package/fakedate/fakedate.mk

@@ -8,8 +8,7 @@
 HOST_FAKEDATE_LICENSE = GPL-2.0+
 
 define HOST_FAKEDATE_INSTALL_CMDS
-	$(INSTALL) -D -m 755 package/fakedate/fakedate $(HOST_DIR)/usr/bin/fakedate
-	ln -sfn fakedate $(HOST_DIR)/usr/bin/date
+	$(INSTALL) -D -m 755 package/fakedate/fakedate $(HOST_DIR)/usr/bin/date
 endef
 
 $(eval $(host-generic-package))