[PATCH 2/7] revision.h: introduce blob/tree walking in order of the commits

[Stefan Beller <sbeller@google.com>]

The functionality to list tree objects in the order they were seen
while traversing the commits will be used in the next commit,
where we teach `git describe` to describe not only commits, but
trees and blobs, too.

Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Stefan Beller <sbeller@google.com>
---
 list-objects.c               |  2 ++
 revision.c                   |  2 ++
 revision.h                   |  3 ++-
 t/t6100-rev-list-in-order.sh | 44 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100755 t/t6100-rev-list-in-order.sh

diff --git a/list-objects.c b/list-objects.c
index bf46f80dff..5e114c9a8a 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -237,6 +237,8 @@ void traverse_commit_list(struct rev_info *revs,
 		if (commit->tree)
 			add_pending_tree(revs, commit->tree);
 		show_commit(commit, data);
+		if (revs->tree_blobs_in_commit_order)
+			traverse_trees_and_blobs(revs, &base_path, show_object, data);
 	}
 	traverse_trees_and_blobs(revs, &base_path, show_object, data);
 
diff --git a/revision.c b/revision.c
index d167223e69..9329d4ebbf 100644
--- a/revision.c
+++ b/revision.c
@@ -1845,6 +1845,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->dense = 0;
 	} else if (!strcmp(arg, "--show-all")) {
 		revs->show_all = 1;
+	} else if (!strcmp(arg, "--in-commit-order")) {
+		revs->tree_blobs_in_commit_order = 1;
 	} else if (!strcmp(arg, "--remove-empty")) {
 		revs->remove_empty_trees = 1;
 	} else if (!strcmp(arg, "--merges")) {
diff --git a/revision.h b/revision.h
index 54761200ad..86985d68aa 100644
--- a/revision.h
+++ b/revision.h
@@ -121,7 +121,8 @@ struct rev_info {
 			bisect:1,
 			ancestry_path:1,
 			first_parent_only:1,
-			line_level_traverse:1;
+			line_level_traverse:1,
+			tree_blobs_in_commit_order:1;
 
 	/* Diff flags */
 	unsigned int	diff:1,
diff --git a/t/t6100-rev-list-in-order.sh b/t/t6100-rev-list-in-order.sh
new file mode 100755
index 0000000000..67ebe815d2
--- /dev/null
+++ b/t/t6100-rev-list-in-order.sh
@@ -0,0 +1,44 @@
+#!/bin/sh
+
+test_description='miscellaneous rev-list tests'
+
+. ./test-lib.sh
+
+
+test_expect_success 'setup' '
+	for x in one two three four
+	do
+		echo $x >$x &&
+		git add $x &&
+		git commit -m "add file $x"
+	done &&
+	for x in four three
+	do
+		git rm $x
+		git commit -m "remove $x"
+	done &&
+	git rev-list --in-commit-order --objects HEAD >actual.raw &&
+	cut -c 1-40 > actual < actual.raw &&
+
+	>expect &&
+	git rev-parse HEAD^{commit}       >>expect &&
+	git rev-parse HEAD^{tree}         >>expect &&
+	git rev-parse HEAD^{tree}:one     >>expect &&
+	git rev-parse HEAD^{tree}:two     >>expect &&
+	git rev-parse HEAD~1^{commit}     >>expect &&
+	git rev-parse HEAD~1^{tree}       >>expect &&
+	git rev-parse HEAD~1^{tree}:three >>expect &&
+	git rev-parse HEAD~2^{commit}     >>expect &&
+	git rev-parse HEAD~2^{tree}       >>expect &&
+	git rev-parse HEAD~2^{tree}:four  >>expect &&
+	git rev-parse HEAD~3^{commit}     >>expect &&
+	# skip HEAD~3^{tree}
+	git rev-parse HEAD~4^{commit}     >>expect &&
+	# skip HEAD~4^{tree}
+	git rev-parse HEAD~5^{commit}     >>expect &&
+	git rev-parse HEAD~5^{tree}       >>expect &&
+
+	test_cmp expect actual
+'
+
+test_done
-- 
2.15.0.rc2.443.gfcc3b81c0a