Description: Informative message when using graph without graphviz
 Previously, trying to use the graph subcommand without graphviz being
 installed resulted in a cryptic error message: 
 .
 Can't exec "tred": No such file or directory at /usr/lib/perl/5.14/IO/File.pm line 66, <STDIN> line 1.
 .
 graphviz is already in the Suggests field of the debian package, and
 we cannot raise this dependency severity given the central role of
 quilt in the debian infrastructure. This informative error message is
 much more sensible.
 .
 Also, merge the error message with the one from quilt mail when
 formail is not installed to ease the life of translators.
Author: Martin Quinson <address@hidden>
Bug-Debian: http://bugs.debian.org/659944
Forwarded: 2014-01-18

---
 quilt/graph.in |   12 ++++++++++++
 quilt/mail.in  |    2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

Index: b/quilt/graph.in
===================================================================
--- a/quilt/graph.in
+++ b/quilt/graph.in
@@ -109,6 +109,18 @@
 	usage
 fi
 
+if [ "$opt_format" = "ps" ] && ! type dot &> /dev/null
+then
+	printf $"You have to install '%s' (from package %s) to use 'quilt %s'." dot graphviz "graph -T"
+	exit 1
+fi
+
+if [ -n "$opt_reduce" ] && ! type tred &> /dev/null
+then
+	printf $"You have to install '%s' (from package %s) to use 'quilt %s'." tred graphviz "graph --reduce"
+	exit 1
+fi
+
 if [ -z "$opt_all" ]
 then
 	patch=$(find_applied_patch "$1") || exit 1
Index: b/quilt/mail.in
===================================================================
--- a/quilt/mail.in
+++ b/quilt/mail.in
@@ -259,7 +259,7 @@
 # check if formail is installed before doing anything
 if ! type formail &> /dev/null
 then
-	echo $"You have to install 'formail' to use 'quilt mail'" >&2
+	printf $"You have to install '%s' (from package %s) to use 'quilt %s'." formail procmail mail >&2
 	exit 1
 fi