[PATCH] cogito: Avoid slowness when timewarping large trees.

[Jeff King <peff@peff.net>]

tree_timewarp was calling read, egrep, and rm in an O(N) loop where N is
the number of changed files between two trees. This caused a bottleneck
when seeking/switching/merging between trees with many changed files.

On the historical linux tree, the time to cg-seek from the head to the
initial commit (a change of 19099 files) dropped from 2m35s to 21s.

---

 cg-Xlib |    9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

a9a160c0bd63973c53ba3aa74650728135d23ac7
diff --git a/cg-Xlib b/cg-Xlib
index a2f28cf..ceddeeb 100644
--- a/cg-Xlib
+++ b/cg-Xlib
@@ -345,12 +345,9 @@ tree_timewarp()
 
 	# Kill gone files
 	git-diff-tree -r "$base" "$branch" |
-		while IFS=$'\t' read header file; do
-			# match ":100755 000000 14d43b1abf... 000000000... D"
-			if echo "$header" | egrep "^:([^ ][^ ]* ){4}D" >/dev/null; then
-				rm -- "$file"
-			fi
-		done
+		# match ":100755 000000 14d43b1abf... 000000000... D"
+		sed -ne 's/^:\([^ ][^ ]* \)\{4\}D\t//p' |
+		xargs rm --
 	git-checkout-index -u -f -a
 
 	# FIXME: Can produce bogus "contains only garbage" messages.
-- 
1.2.4