diff --git a/t/t0006-date.sh b/t/t0006-date.sh
index 1d29810a7a..e53cf6d36d 100755
--- a/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@ -11,7 +11,7 @@ check_show() {
 	echo "$t -> $2" >expect
 	test_expect_${3:-success} "relative date ($2)" "
 	test-date show $t >actual &&
-	test_cmp expect actual
+	test_i18ncmp expect actual
 	"
 }
 
diff --git a/t/t0040-parse-options.sh b/t/t0040-parse-options.sh
index e3f354a45e..244a43c920 100755
--- a/t/t0040-parse-options.sh
+++ b/t/t0040-parse-options.sh
@@ -51,7 +51,7 @@ EOF
 test_expect_success 'test help' '
 	test_must_fail test-parse-options -h > output 2> output.err &&
 	test ! -s output.err &&
-	test_cmp expect output
+	test_i18ncmp expect output
 '
 
 mv expect expect.err
@@ -79,6 +79,17 @@ check() {
 	test_cmp expect output
 }
 
+check_i18n() {
+	what="$1" &&
+	shift &&
+	expect="$1" &&
+	shift &&
+	sed "s/^$what .*/$what $expect/" <expect.template >expect &&
+	test-parse-options $* >output 2>output.err &&
+	test ! -s output.err &&
+	test_i18ncmp expect output
+}
+
 check_unknown() {
 	case "$1" in
 	--*)
@@ -92,6 +103,19 @@ check_unknown() {
 	test_cmp expect output.err
 }
 
+check_unknown_i18n() {
+	case "$1" in
+	--*)
+		echo error: unknown option \`${1#--}\' >expect ;;
+	-*)
+		echo error: unknown switch \`${1#-}\' >expect ;;
+	esac &&
+	cat expect.err >>expect &&
+	test_must_fail test-parse-options $* >output 2>output.err &&
+	test ! -s output &&
+	test_i18ncmp expect output.err
+}
+
 test_expect_success 'OPT_BOOL() #1' 'check boolean: 1 --yes'
 test_expect_success 'OPT_BOOL() #2' 'check boolean: 1 --no-doubt'
 test_expect_success 'OPT_BOOL() #3' 'check boolean: 1 -D'
@@ -104,8 +128,8 @@ test_expect_success 'OPT_BOOL() is idempotent #2' 'check boolean: 1 -DB'
 test_expect_success 'OPT_BOOL() negation #1' 'check boolean: 0 -D --no-yes'
 test_expect_success 'OPT_BOOL() negation #2' 'check boolean: 0 -D --no-no-doubt'
 
-test_expect_success 'OPT_BOOL() no negation #1' 'check_unknown --fear'
-test_expect_success 'OPT_BOOL() no negation #2' 'check_unknown --no-no-fear'
+test_expect_success 'OPT_BOOL() no negation #1' 'check_unknown_i18n --fear'
+test_expect_success 'OPT_BOOL() no negation #2' 'check_unknown_i18n --no-no-fear'
 
 test_expect_success 'OPT_BOOL() positivation' 'check boolean: 0 -D --doubt'
 
@@ -310,8 +334,8 @@ EOF
 
 test_expect_success 'OPT_CALLBACK() and callback errors work' '
 	test_must_fail test-parse-options --no-length > output 2> output.err &&
-	test_cmp expect output &&
-	test_cmp expect.err output.err
+	test_i18ncmp expect output &&
+	test_i18ncmp expect.err output.err
 '
 
 cat > expect <<EOF
diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index a477453e2e..e127f35db9 100755
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -391,7 +391,7 @@ test_expect_success 'get bool variable with empty value' \
 
 test_expect_success 'no arguments, but no crash' '
 	test_must_fail git config >output 2>&1 &&
-	grep usage output
+	test_i18ngrep usage output
 '
 
 cat > .git/config << EOF
diff --git a/t/t1502-rev-parse-parseopt.sh b/t/t1502-rev-parse-parseopt.sh
index 1efd7f76dd..13c88c9aae 100755
--- a/t/t1502-rev-parse-parseopt.sh
+++ b/t/t1502-rev-parse-parseopt.sh
@@ -41,7 +41,7 @@ EOF
 
 test_expect_success 'test --parseopt help output' '
 	test_expect_code 129 git rev-parse --parseopt -- -h > output < optionspec &&
-	test_cmp expect output
+	test_i18ncmp expect output
 '
 
 cat > expect <<EOF
diff --git a/t/t2006-checkout-index-basic.sh b/t/t2006-checkout-index-basic.sh
index b8559838b1..57cbdfe9bc 100755
--- a/t/t2006-checkout-index-basic.sh
+++ b/t/t2006-checkout-index-basic.sh
@@ -7,7 +7,7 @@ test_description='basic checkout-index tests
 
 test_expect_success 'checkout-index --gobbledegook' '
 	test_expect_code 129 git checkout-index --gobbledegook 2>err &&
-	grep "[Uu]sage" err
+	test_i18ngrep "[Uu]sage" err
 '
 
 test_expect_success 'checkout-index -h in broken repository' '
@@ -18,7 +18,7 @@ test_expect_success 'checkout-index -h in broken repository' '
 		>.git/index &&
 		test_expect_code 129 git checkout-index -h >usage 2>&1
 	) &&
-	grep "[Uu]sage" broken/usage
+	test_i18ngrep "[Uu]sage" broken/usage
 '
 
 test_done
diff --git a/t/t2107-update-index-basic.sh b/t/t2107-update-index-basic.sh
index 0dbbb00d74..a6405d318d 100755
--- a/t/t2107-update-index-basic.sh
+++ b/t/t2107-update-index-basic.sh
@@ -15,7 +15,7 @@ test_expect_success 'update-index --nonsense fails' '
 
 test_expect_success 'update-index --nonsense dumps usage' '
 	test_expect_code 129 git update-index --nonsense 2>err &&
-	grep "[Uu]sage: git update-index" err
+	test_i18ngrep "[Uu]sage: git update-index" err
 '
 
 test_expect_success 'update-index -h with corrupt index' '
@@ -26,7 +26,7 @@ test_expect_success 'update-index -h with corrupt index' '
 		>.git/index &&
 		test_expect_code 129 git update-index -h >usage 2>&1
 	) &&
-	grep "[Uu]sage: git update-index" broken/usage
+	test_i18ngrep "[Uu]sage: git update-index" broken/usage
 '
 
 test_expect_success '--cacheinfo does not accept blob null sha1' '
diff --git a/t/t3004-ls-files-basic.sh b/t/t3004-ls-files-basic.sh
index 490e052875..8d9bc3c2af 100755
--- a/t/t3004-ls-files-basic.sh
+++ b/t/t3004-ls-files-basic.sh
@@ -22,7 +22,7 @@ test_expect_success 'ls-files with nonexistent path' '
 
 test_expect_success 'ls-files with nonsense option' '
 	test_expect_code 129 git ls-files --nonsense 2>actual &&
-	grep "[Uu]sage: git ls-files" actual
+	test_i18ngrep "[Uu]sage: git ls-files" actual
 '
 
 test_expect_success 'ls-files -h in corrupt repository' '
@@ -33,7 +33,7 @@ test_expect_success 'ls-files -h in corrupt repository' '
 		>.git/index &&
 		test_expect_code 129 git ls-files -h >usage 2>&1
 	) &&
-	grep "[Uu]sage: git ls-files " broken/usage
+	test_i18ngrep "[Uu]sage: git ls-files " broken/usage
 '
 
 test_done
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index a17f8b2a40..1ffce2173e 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -31,7 +31,7 @@ test_expect_success 'branch -h in broken repository' '
 		>.git/refs/heads/master &&
 		test_expect_code 129 git branch -h >usage 2>&1
 	) &&
-	grep "[Uu]sage" broken/usage
+	test_i18ngrep "[Uu]sage" broken/usage
 '
 
 test_expect_success \
@@ -74,7 +74,7 @@ test_expect_success \
 test_expect_success \
     'git branch -m dumps usage' \
        'test_expect_code 129 git branch -m 2>err &&
-	grep "[Uu]sage: git branch" err'
+	test_i18ngrep "[Uu]sage: git branch" err'
 
 test_expect_success \
     'git branch -m m m/m should work' \
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index 595d2ff990..34c86e5de6 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -47,7 +47,7 @@ test_expect_success 'cherry-pick --nonsense' '
 	git diff --exit-code HEAD &&
 	test_must_fail git cherry-pick --nonsense 2>msg &&
 	git diff --exit-code HEAD "$pos" &&
-	grep '[Uu]sage:' msg
+	test_i18ngrep '[Uu]sage:' msg
 '
 
 test_expect_success 'revert --nonsense' '
@@ -56,7 +56,7 @@ test_expect_success 'revert --nonsense' '
 	git diff --exit-code HEAD &&
 	test_must_fail git revert --nonsense 2>msg &&
 	git diff --exit-code HEAD "$pos" &&
-	grep '[Uu]sage:' msg
+	test_i18ngrep '[Uu]sage:' msg
 '
 
 test_expect_success 'cherry-pick after renaming branch' '
diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
index cd042633ba..5dfbda7491 100755
--- a/t/t3903-stash.sh
+++ b/t/t3903-stash.sh
@@ -610,7 +610,7 @@ test_expect_success 'stash apply shows status same as git status (relative to cu
 		git stash apply
 	) |
 	sed -e 1,2d >actual && # drop "Saved..." and "HEAD is now..."
-	test_cmp expect actual
+	test_i18ncmp expect actual
 '
 
 cat > expect << EOF
diff --git a/t/t4006-diff-mode.sh b/t/t4006-diff-mode.sh
index 7a3e1f9a24..3d4b1ba23f 100755
--- a/t/t4006-diff-mode.sh
+++ b/t/t4006-diff-mode.sh
@@ -36,24 +36,24 @@ test_expect_success '--stat output after text chmod' '
 	test_chmod -x rezrov &&
 	echo " 0 files changed" >expect &&
 	git diff HEAD --stat >actual &&
-	test_cmp expect actual
+	test_i18ncmp expect actual
 '
 
 test_expect_success '--shortstat output after text chmod' '
 	git diff HEAD --shortstat >actual &&
-	test_cmp expect actual
+	test_i18ncmp expect actual
 '
 
 test_expect_success '--stat output after binary chmod' '
 	test_chmod +x binbin &&
 	echo " 0 files changed" >expect &&
 	git diff HEAD --stat >actual &&
-	test_cmp expect actual
+	test_i18ncmp expect actual
 '
 
 test_expect_success '--shortstat output after binary chmod' '
 	git diff HEAD --shortstat >actual &&
-	test_cmp expect actual
+	test_i18ncmp expect actual
 '
 
 test_done
diff --git a/t/t4012-diff-binary.sh b/t/t4012-diff-binary.sh
index ec4deea192..1215ae544b 100755
--- a/t/t4012-diff-binary.sh
+++ b/t/t4012-diff-binary.sh
@@ -63,7 +63,7 @@ test_expect_success 'apply --numstat understands diff --binary format' '
 
 # apply needs to be able to skip the binary material correctly
 # in order to report the line number of a corrupt patch.
-test_expect_success 'apply detecting corrupt patch correctly' '
+test_expect_success C_LOCALE_OUTPUT 'apply detecting corrupt patch correctly' '
 	git diff >output &&
 	sed -e "s/-CIT/xCIT/" <output >broken &&
 	test_must_fail git apply --stat --summary broken 2>detected &&
@@ -73,7 +73,7 @@ test_expect_success 'apply detecting corrupt patch correctly' '
 	test "$detected" = xCIT
 '
 
-test_expect_success 'apply detecting corrupt patch correctly' '
+test_expect_success C_LOCALE_OUTPUT 'apply detecting corrupt patch correctly' '
 	git diff --binary | sed -e "s/-CIT/xCIT/" >broken &&
 	test_must_fail git apply --stat --summary broken 2>detected &&
 	detected=`cat detected` &&
diff --git a/t/t4120-apply-popt.sh b/t/t4120-apply-popt.sh
index a33d510bf6..c5fecdfed4 100755
--- a/t/t4120-apply-popt.sh
+++ b/t/t4120-apply-popt.sh
@@ -32,7 +32,7 @@ test_expect_success 'apply git diff with -p2' '
 test_expect_success 'apply with too large -p' '
 	cp file1.saved file1 &&
 	test_must_fail git apply --stat -p3 patch.file 2>err &&
-	grep "removing 3 leading" err
+	test_i18ngrep "removing 3 leading" err
 '
 
 test_expect_success 'apply (-p2) traditional diff with funny filenames' '
@@ -54,7 +54,7 @@ test_expect_success 'apply (-p2) traditional diff with funny filenames' '
 test_expect_success 'apply with too large -p and fancy filename' '
 	cp file1.saved file1 &&
 	test_must_fail git apply --stat -p3 patch.escaped 2>err &&
-	grep "removing 3 leading" err
+	test_i18ngrep "removing 3 leading" err
 '
 
 test_expect_success 'apply (-p2) diff, mode change only' '
diff --git a/t/t4133-apply-filenames.sh b/t/t4133-apply-filenames.sh
index 94da99075c..2ecb4216b7 100755
--- a/t/t4133-apply-filenames.sh
+++ b/t/t4133-apply-filenames.sh
@@ -30,9 +30,9 @@ EOF
 
 test_expect_success 'apply diff with inconsistent filenames in headers' '
 	test_must_fail git apply bad1.patch 2>err &&
-	grep "inconsistent new filename" err &&
+	test_i18ngrep "inconsistent new filename" err &&
 	test_must_fail git apply bad2.patch 2>err &&
-	grep "inconsistent old filename" err
+	test_i18ngrep "inconsistent old filename" err
 '
 
 test_done
diff --git a/t/t4200-rerere.sh b/t/t4200-rerere.sh
index 3ab670d36a..7f6666fcd3 100755
--- a/t/t4200-rerere.sh
+++ b/t/t4200-rerere.sh
@@ -382,13 +382,13 @@ test_expect_success 'rerere --no-no-rerere-autoupdate' '
 	git update-index --index-info <failedmerge &&
 	cp file3.conflict file3 &&
 	test_must_fail git rerere --no-no-rerere-autoupdate 2>err &&
-	grep [Uu]sage err &&
+	test_i18ngrep [Uu]sage err &&
 	test_must_fail git update-index --refresh
 '
 
 test_expect_success 'rerere -h' '
 	test_must_fail git rerere -h >help &&
-	grep [Uu]sage help
+	test_i18ngrep [Uu]sage help
 '
 
 test_done
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index 71be59d446..31869dc0db 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -803,7 +803,7 @@ sanitize_output () {
 test_expect_success 'log --graph with diff and stats' '
 	git log --graph --pretty=short --stat -p >actual &&
 	sanitize_output >actual.sanitized <actual &&
-	test_cmp expect actual.sanitized
+	test_i18ncmp expect actual.sanitized
 '
 
 test_done
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 4afd77815f..2c45de7aea 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -88,7 +88,7 @@ test_expect_success 'NUL separation with --stat' '
 	stat1_part=$(git diff --stat --root HEAD^) &&
 	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n" >expected &&
 	git log -z --stat --pretty="format:%s" >actual &&
-	test_cmp expected actual
+	test_i18ncmp expected actual
 '
 
 test_expect_failure 'NUL termination with --stat' '
@@ -96,7 +96,7 @@ test_expect_failure 'NUL termination with --stat' '
 	stat1_part=$(git diff --stat --root HEAD^) &&
 	printf "add bar\n$stat0_part\n\0initial\n$stat1_part\n\0" >expected &&
 	git log -z --stat --pretty="tformat:%s" >actual &&
-	test_cmp expected actual
+	test_i18ncmp expected actual
 '
 
 test_done
diff --git a/t/t5300-pack-object.sh b/t/t5300-pack-object.sh
index 2e52f8b838..a07c871797 100755
--- a/t/t5300-pack-object.sh
+++ b/t/t5300-pack-object.sh
@@ -416,11 +416,11 @@ test_expect_success \
 test_expect_success \
     'make sure index-pack detects the SHA1 collision' \
     'test_must_fail git index-pack -o bad.idx test-3.pack 2>msg &&
-     grep "SHA1 COLLISION FOUND" msg'
+     test_i18ngrep "SHA1 COLLISION FOUND" msg'
 
 test_expect_success \
     'make sure index-pack detects the SHA1 collision (large blobs)' \
     'test_must_fail git -c core.bigfilethreshold=1 index-pack -o bad.idx test-3.pack 2>msg &&
-     grep "SHA1 COLLISION FOUND" msg'
+     test_i18ngrep "SHA1 COLLISION FOUND" msg'
 
 test_done
diff --git a/t/t5505-remote.sh b/t/t5505-remote.sh
index e8af615e6d..88a21ff0bf 100755
--- a/t/t5505-remote.sh
+++ b/t/t5505-remote.sh
@@ -52,7 +52,7 @@ test_expect_success setup '
 
 '
 
-test_expect_success 'remote information for the origin' '
+test_expect_success C_LOCALE_OUTPUT 'remote information for the origin' '
 (
 	cd test &&
 	tokens_match origin "$(git remote)" &&
@@ -66,8 +66,6 @@ test_expect_success 'add another remote' '
 	cd test &&
 	git remote add -f second ../two &&
 	tokens_match "origin second" "$(git remote)" &&
-	check_remote_track origin master side &&
-	check_remote_track second master side another &&
 	check_tracking_branch second master side another &&
 	git for-each-ref "--format=%(refname)" refs/remotes |
 	sed -e "/^refs\/remotes\/origin\//d" \
@@ -77,6 +75,14 @@ test_expect_success 'add another remote' '
 )
 '
 
+test_expect_success C_LOCALE_OUTPUT 'check remote tracking' '
+(
+	cd test &&
+	check_remote_track origin master side &&
+	check_remote_track second master side another
+)
+'
+
 test_expect_success 'remote forces tracking branches' '
 (
 	cd test &&
@@ -95,7 +101,7 @@ test_expect_success 'remove remote' '
 )
 '
 
-test_expect_success 'remove remote' '
+test_expect_success C_LOCALE_OUTPUT 'remove remote' '
 (
 	cd test &&
 	tokens_match origin "$(git remote)" &&
@@ -131,8 +137,8 @@ EOF
 	git remote rm oops 2>actual2 &&
 	git branch -d foobranch &&
 	git tag -d footag &&
-	test_cmp expect1 actual1 &&
-	test_cmp expect2 actual2
+	test_i18ncmp expect1 actual1 &&
+	test_i18ncmp expect2 actual2
 )
 '
 
@@ -192,7 +198,7 @@ test_expect_success 'show' '
 	 git config --add remote.two.push refs/heads/master:refs/heads/another &&
 	 git remote show origin two > output &&
 	 git branch -d rebase octopus &&
-	 test_cmp expect output)
+	 test_i18ncmp expect output)
 '
 
 cat > test/expect << EOF
@@ -217,7 +223,7 @@ test_expect_success 'show -n' '
 	 cd test &&
 	 git remote show -n origin > output &&
 	 mv ../one.unreachable ../one &&
-	 test_cmp expect output)
+	 test_i18ncmp expect output)
 '
 
 test_expect_success 'prune' '
@@ -255,7 +261,7 @@ EOF
 test_expect_success 'set-head --auto fails w/multiple HEADs' '
 	(cd test &&
 	 test_must_fail git remote set-head --auto two >output 2>&1 &&
-	test_cmp expect output)
+	test_i18ncmp expect output)
 '
 
 cat >test/expect <<EOF
@@ -285,7 +291,7 @@ test_expect_success 'prune --dry-run' '
 	 test_must_fail git rev-parse refs/remotes/origin/side &&
 	(cd ../one &&
 	 git branch -m side side2) &&
-	 test_cmp expect output)
+	 test_i18ncmp expect output)
 '
 
 test_expect_success 'add --mirror && prune' '
@@ -705,7 +711,7 @@ test_expect_success 'remote prune to cause a dangling symref' '
 		cd seven &&
 		git remote prune origin
 	) >err 2>&1 &&
-	grep "has become dangling" err &&
+	test_i18ngrep "has become dangling" err &&
 
 	: And the dangling symref will not cause other annoying errors &&
 	(
diff --git a/t/t5530-upload-pack-error.sh b/t/t5530-upload-pack-error.sh
index 6b2a5f4a65..c983d3694c 100755
--- a/t/t5530-upload-pack-error.sh
+++ b/t/t5530-upload-pack-error.sh
@@ -35,8 +35,8 @@ test_expect_success 'upload-pack fails due to error in pack-objects packing' '
 	printf "0032want %s\n00000009done\n0000" \
 		$(git rev-parse HEAD) >input &&
 	test_must_fail git upload-pack . <input >/dev/null 2>output.err &&
-	grep "unable to read" output.err &&
-	grep "pack-objects died" output.err
+	test_i18ngrep "unable to read" output.err &&
+	test_i18ngrep "pack-objects died" output.err
 '
 
 test_expect_success 'corrupt repo differently' '
diff --git a/t/t6500-gc.sh b/t/t6500-gc.sh
index 82f3639937..b1a63655f9 100755
--- a/t/t6500-gc.sh
+++ b/t/t6500-gc.sh
@@ -11,7 +11,7 @@ test_expect_success 'gc empty repository' '
 
 test_expect_success 'gc --gobbledegook' '
 	test_expect_code 129 git gc --nonsense 2>err &&
-	grep "[Uu]sage: git gc" err
+	test_i18ngrep "[Uu]sage: git gc" err
 '
 
 test_expect_success 'gc -h with invalid configuration' '
@@ -22,7 +22,7 @@ test_expect_success 'gc -h with invalid configuration' '
 		echo "[gc] pruneexpire = CORRUPT" >>.git/config &&
 		test_expect_code 129 git gc -h >usage 2>&1
 	) &&
-	grep "[Uu]sage" broken/usage
+	test_i18ngrep "[Uu]sage" broken/usage
 '
 
 test_done
diff --git a/t/t7508-status.sh b/t/t7508-status.sh
index c206f4777a..e313ef196e 100755
--- a/t/t7508-status.sh
+++ b/t/t7508-status.sh
@@ -80,7 +80,7 @@ test_expect_success 'status --column' '
 #	dir1/untracked dir2/untracked untracked
 #	dir2/modified  output
 EOF
-	test_cmp expect output
+	test_i18ncmp expect output
 '
 
 cat >expect <<\EOF
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index 9e27bbf902..5e19598fe7 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -157,7 +157,7 @@ test_expect_success 'merge -h with invalid index' '
 		>.git/index &&
 		test_expect_code 129 git merge -h 2>usage
 	) &&
-	grep "[Uu]sage: git merge" broken/usage
+	test_i18ngrep "[Uu]sage: git merge" broken/usage
 '
 
 test_expect_success 'reject non-strategy with a git-merge-foo name' '