If someone provides a --prefix that ends with slash, strip the slash.

Prefixes that differ only in the trailing slash should be considered
identical.

Also update the test to check that this works.

git-subtree.sh

@@ -102,7 +102,7 @@ esac
 if [ -z "$prefix" ]; then
 	die "You must provide the --prefix option."
 fi
-dir="$prefix"
+dir="$(dirname "$prefix/.")"
 
 if [ "$command" != "pull" ]; then
 	revs=$(git rev-parse $default --revs-only "$@") || exit $?
@@ -175,7 +175,7 @@ find_latest_squash()
 	sq=
 	main=
 	sub=
-	git log --grep="^git-subtree-dir: $dir\$" \
+	git log --grep="^git-subtree-dir: $dir/*\$" \
 		--pretty=format:'START %H%n%s%n%n%b%nEND%n' HEAD |
 	while read a b junk; do
 		debug "$a $b $junk"
@@ -210,7 +210,7 @@ find_existing_splits()
 	revs="$2"
 	main=
 	sub=
-	git log --grep="^git-subtree-dir: $dir\$" \
+	git log --grep="^git-subtree-dir: $dir/*\$" \
 		--pretty=format:'START %H%n%s%n%n%b%nEND%n' $revs |
 	while read a b junk; do
 		case "$a" in

test.sh

@@ -82,7 +82,7 @@ git branch subdir
 
 git fetch ../subproj sub1
 git branch sub1 FETCH_HEAD
-git subtree add --prefix=subdir FETCH_HEAD
+git subtree add --prefix=subdir/ FETCH_HEAD
 
 # this shouldn't actually do anything, since FETCH_HEAD is already a parent
 git merge -m 'merge -s -ours' -s ours FETCH_HEAD
@@ -118,7 +118,7 @@ create sub9
 git commit -m 'sub9'
 
 cd ../mainline
-split2=$(git subtree split --annotate='*' --prefix subdir --rejoin)
+split2=$(git subtree split --annotate='*' --prefix subdir/ --rejoin)
 git branch split2 "$split2"
 
 create subdir/main-sub10

todo

@@ -36,10 +36,6 @@
 		one of the other git tools that git-subtree calls.  Should
 		detect this situation and print the *real* problem.
 	
-	In fact, the prefix should *not* end with slash, and we
-		should detect (and fix) it if it does.  Otherwise the
-		log message looks weird.
-		
 	"pull --squash" should do fetch-synthesize-merge, but instead just
 		does "pull" directly, which doesn't work at all.