t5318: extract helpers to lib-commit-graph.sh

The graph_git_behavior helper is useful for testing that certain Git
commands behave the same when using the commit-graph and when not using
the commit-graph. Extract it to a new lib-commit-graph.sh file for use
in new test scripts that will split out from t5318.

While doing this extraction, also extract graph_read_expect and the
logic for priming the test_oid_cache.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-commit-graph.sh

@@ -0,0 +1,48 @@
+#!/bin/sh
+
+# Helper functions for testing commit-graphs.
+
+# Initialize OID cache with oid_version
+test_oid_cache <<-EOF
+oid_version sha1:1
+oid_version sha256:2
+EOF
+
+graph_git_two_modes() {
+	git -c core.commitGraph=true $1 >output &&
+	git -c core.commitGraph=false $1 >expect &&
+	test_cmp expect output
+}
+
+graph_git_behavior() {
+	MSG=$1
+	DIR=$2
+	BRANCH=$3
+	COMPARE=$4
+	test_expect_success "check normal git operations: $MSG" '
+		cd "$TRASH_DIRECTORY/$DIR" &&
+		graph_git_two_modes "log --oneline $BRANCH" &&
+		graph_git_two_modes "log --topo-order $BRANCH" &&
+		graph_git_two_modes "log --graph $COMPARE..$BRANCH" &&
+		graph_git_two_modes "branch -vv" &&
+		graph_git_two_modes "merge-base -a $BRANCH $COMPARE"
+	'
+}
+
+graph_read_expect() {
+	OPTIONAL=""
+	NUM_CHUNKS=3
+	if test -n "$2"
+	then
+		OPTIONAL=" $2"
+		NUM_CHUNKS=$((3 + $(echo "$2" | wc -w)))
+	fi
+	cat >expect <<- EOF
+	header: 43475048 1 $(test_oid oid_version) $NUM_CHUNKS 0
+	num_commits: $1
+	chunks: oid_fanout oid_lookup commit_metadata$OPTIONAL
+	options:
+	EOF
+	test-tool read-graph >output &&
+	test_cmp expect output
+}

t/t5318-commit-graph.sh

@@ -29,12 +29,7 @@ test_expect_success 'setup full repo' '
 	cd "$TRASH_DIRECTORY/full" &&
 	git init &&
 	git config core.commitGraph true &&
-	objdir=".git/objects" &&
-
-	test_oid_cache <<-EOF
-	oid_version sha1:1
-	oid_version sha256:2
-	EOF
+	objdir=".git/objects"
 '
 
 test_expect_success POSIXPERM 'tweak umask for modebit tests' '
@@ -69,47 +64,10 @@ test_expect_success 'create commits and repack' '
 	git repack
 '
 
-graph_git_two_modes() {
-	git -c core.commitGraph=true $1 >output &&
-	git -c core.commitGraph=false $1 >expect &&
-	test_cmp expect output
-}
-
-graph_git_behavior() {
-	MSG=$1
-	DIR=$2
-	BRANCH=$3
-	COMPARE=$4
-	test_expect_success "check normal git operations: $MSG" '
-		cd "$TRASH_DIRECTORY/$DIR" &&
-		graph_git_two_modes "log --oneline $BRANCH" &&
-		graph_git_two_modes "log --topo-order $BRANCH" &&
-		graph_git_two_modes "log --graph $COMPARE..$BRANCH" &&
-		graph_git_two_modes "branch -vv" &&
-		graph_git_two_modes "merge-base -a $BRANCH $COMPARE"
-	'
-}
+. "$TEST_DIRECTORY"/lib-commit-graph.sh
 
 graph_git_behavior 'no graph' full commits/3 commits/1
 
-graph_read_expect() {
-	OPTIONAL=""
-	NUM_CHUNKS=3
-	if test ! -z "$2"
-	then
-		OPTIONAL=" $2"
-		NUM_CHUNKS=$((3 + $(echo "$2" | wc -w)))
-	fi
-	cat >expect <<- EOF
-	header: 43475048 1 $(test_oid oid_version) $NUM_CHUNKS 0
-	num_commits: $1
-	chunks: oid_fanout oid_lookup commit_metadata$OPTIONAL
-	options:
-	EOF
-	test-tool read-graph >output &&
-	test_cmp expect output
-}
-
 test_expect_success 'exit with correct error on bad input to --stdin-commits' '
 	cd "$TRASH_DIRECTORY/full" &&
 	# invalid, non-hex OID
@@ -826,10 +784,6 @@ test_expect_success 'set up and verify repo with generation data overflow chunk'
 	objdir=".git/objects" &&
 	UNIX_EPOCH_ZERO="@0 +0000" &&
 	FUTURE_DATE="@2147483646 +0000" &&
-	test_oid_cache <<-EOF &&
-	oid_version sha1:1
-	oid_version sha256:2
-	EOF
 	cd "$TRASH_DIRECTORY" &&
 	mkdir repo &&
 	cd repo &&