pull: clarify advice for the unconfigured error case

When pull --rebase fails because it cannot find what branch to
merge against, the error message implies we are trying to merge.
Say "rebase against" instead of "merge with" to avoid confusion.

The configuration suggested to remedy the situation uses a
confusing syntax, with variables specified in the dotted form
accepted by 'git config' but separated from their values by the
'=' delimiter used by config files.  Since the user will have to
edit this output anyway, it is more helpful to provide a config
file snippet to paste into an editor and modify.

Signed-off-by: Jan Krüger <jk@jk.gs>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-pull.sh

@@ -88,45 +88,63 @@ error_on_no_merge_candidates () {
 		esac
 	done
 
+	if test true = "$rebase"
+	then
+		op_type=rebase
+		op_prep=against
+	else
+		op_type=merge
+		op_prep=with
+	fi
+
 	curr_branch=${curr_branch#refs/heads/}
 	upstream=$(git config "branch.$curr_branch.merge")
 	remote=$(git config "branch.$curr_branch.remote")
 
 	if [ $# -gt 1 ]; then
-		echo "There are no candidates for merging in the refs that you just fetched."
+		if [ "$rebase" = true ]; then
+			printf "There is no candidate for rebasing against "
+		else
+			printf "There are no candidates for merging "
+		fi
+		echo "among the refs that you just fetched."
 		echo "Generally this means that you provided a wildcard refspec which had no"
 		echo "matches on the remote end."
 	elif [ $# -gt 0 ] && [ "$1" != "$remote" ]; then
 		echo "You asked to pull from the remote '$1', but did not specify"
-		echo "a branch to merge. Because this is not the default configured remote"
+		echo "a branch. Because this is not the default configured remote"
 		echo "for your current branch, you must specify a branch on the command line."
 	elif [ -z "$curr_branch" ]; then
 		echo "You are not currently on a branch, so I cannot use any"
 		echo "'branch.<branchname>.merge' in your configuration file."
-		echo "Please specify which branch you want to merge on the command"
+		echo "Please specify which remote branch you want to use on the command"
 		echo "line and try again (e.g. 'git pull <repository> <refspec>')."
 		echo "See git-pull(1) for details."
 	elif [ -z "$upstream" ]; then
 		echo "You asked me to pull without telling me which branch you"
-		echo "want to merge with, and 'branch.${curr_branch}.merge' in"
-		echo "your configuration file does not tell me either.	Please"
-		echo "specify which branch you want to merge on the command line and"
+		echo "want to $op_type $op_prep, and 'branch.${curr_branch}.merge' in"
+		echo "your configuration file does not tell me, either. Please"
+		echo "specify which branch you want to use on the command line and"
 		echo "try again (e.g. 'git pull <repository> <refspec>')."
 		echo "See git-pull(1) for details."
 		echo
-		echo "If you often merge with the same branch, you may want to"
-		echo "configure the following variables in your configuration"
-		echo "file:"
+		echo "If you often $op_type $op_prep the same branch, you may want to"
+		echo "use something like the following in your configuration file:"
+		echo
+		echo "    [branch \"${curr_branch}\"]"
+		echo "    remote = <nickname>"
+		echo "    merge = <remote-ref>"
+		test rebase = "$op_type" &&
+			echo "    rebase = true"
 		echo
-		echo "    branch.${curr_branch}.remote = <nickname>"
-		echo "    branch.${curr_branch}.merge = <remote-ref>"
-		echo "    remote.<nickname>.url = <url>"
-		echo "    remote.<nickname>.fetch = <refspec>"
+		echo "    [remote \"<nickname>\"]"
+		echo "    url = <url>"
+		echo "    fetch = <refspec>"
 		echo
 		echo "See git-config(1) for details."
 	else
-		echo "Your configuration specifies to merge the ref '${upstream#refs/heads/}' from the"
-		echo "remote, but no such ref was fetched."
+		echo "Your configuration specifies to $op_type $op_prep the ref '${upstream#refs/heads/}'"
+		echo "from the remote, but no such ref was fetched."
 	fi
 	exit 1
 }