[PATCH 10/14] packed-graph: teach git-graph --delete-expired

[Derrick Stolee <stolee@gmail.com>]

Teach git-graph to delete the graph previously referenced by 'graph_head'
when writing a new graph file and updating 'graph_head'. This prevents
data creep by storing a list of useless graphs. Be careful to not delete
the graph if the file did not change.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-graph.txt |  8 ++++++--
 builtin/graph.c             | 14 +++++++++++++-
 t/t5319-graph.sh            | 37 +++++++++++++++++++++++++++++++++++--
 3 files changed, 54 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-graph.txt b/Documentation/git-graph.txt
index f690699570..f4f1048d28 100644
--- a/Documentation/git-graph.txt
+++ b/Documentation/git-graph.txt
@@ -39,6 +39,10 @@ OPTIONS
 	When used with --write, update the graph-head file to point to
 	the written graph file.
 
+--delete-expired::
+	When used with --write and --update-head, delete the graph file
+	previously referenced by graph-head.
+
 EXAMPLES
 --------
 
@@ -55,10 +59,10 @@ $ git graph --write
 ------------------------------------------------
 
 * Write a graph file for the packed commits in your local .git folder,
-* and update graph-head.
+* update graph-head, and delete the old graph-<oid>.graph file.
 +
 ------------------------------------------------
-$ git graph --write --update-head
+$ git graph --write --update-head --delete-expired
 ------------------------------------------------
 
 * Read basic information from a graph file.
diff --git a/builtin/graph.c b/builtin/graph.c
index ac15febc46..adf779b601 100644
--- a/builtin/graph.c
+++ b/builtin/graph.c
@@ -12,7 +12,7 @@ static char const * const builtin_graph_usage[] ={
 	N_("git graph [--pack-dir <packdir>]"),
 	N_("git graph --clear [--pack-dir <packdir>]"),
 	N_("git graph --read [--graph-id=<oid>]"),
-	N_("git graph --write [--pack-dir <packdir>] [--update-head]"),
+	N_("git graph --write [--pack-dir <packdir>] [--update-head] [--delete-expired]"),
 	NULL
 };
 
@@ -23,6 +23,7 @@ static struct opts_graph {
 	const char *graph_id;
 	int write;
 	int update_head;
+	int delete_expired;
 	int has_existing;
 	struct object_id old_graph_oid;
 } opts;
@@ -120,6 +121,15 @@ static int graph_write(void)
 	if (graph_id)
 		printf("%s\n", oid_to_hex(graph_id));
 
+	if (opts.delete_expired && opts.update_head && opts.has_existing &&
+	    oidcmp(graph_id, &opts.old_graph_oid)) {
+		char *old_path = get_graph_filename_oid(opts.pack_dir, &opts.old_graph_oid);
+		if (remove_path(old_path))
+			die("failed to remove path %s", old_path);
+
+		free(old_path);
+	}
+
 	free(graph_id);
 	return 0;
 }
@@ -138,6 +148,8 @@ int cmd_graph(int argc, const char **argv, const char *prefix)
 			N_("write graph file")),
 		OPT_BOOL('u', "update-head", &opts.update_head,
 			N_("update graph-head to written graph file")),
+		OPT_BOOL('d', "delete-expired", &opts.delete_expired,
+			N_("delete expired head graph file")),
 		{ OPTION_STRING, 'M', "graph-id", &opts.graph_id,
 			N_("oid"),
 			N_("An OID for a specific graph file in the pack-dir."),
diff --git a/t/t5319-graph.sh b/t/t5319-graph.sh
index 311fb9dd67..a70c7bbb02 100755
--- a/t/t5319-graph.sh
+++ b/t/t5319-graph.sh
@@ -80,9 +80,42 @@ test_expect_success 'write graph with merges' \
      _graph_read_expect "18" "${packdir}" &&
      cmp expect output'
 
+test_expect_success 'Add more commits' \
+    'git reset --hard commits/3 &&
+     for i in $(test_seq 16 20)
+     do
+        git commit --allow-empty -m "commit $i" &&
+        git branch commits/$i
+     done &&
+     git repack'
+
+test_expect_success 'write graph with merges' \
+    'graph3=$(git graph --write --update-head --delete-expired) &&
+     test_path_is_file ${packdir}/graph-${graph3}.graph &&
+     test_path_is_missing ${packdir}/graph-${graph2}.graph &&
+     test_path_is_file ${packdir}/graph-${graph1}.graph &&
+     test_path_is_file ${packdir}/graph-head &&
+     echo ${graph3} >expect &&
+     cmp -n 40 expect ${packdir}/graph-head &&
+     git graph --read --graph-id=${graph3} >output &&
+     _graph_read_expect "23" "${packdir}" &&
+     cmp expect output'
+
+test_expect_success 'write graph with nothing new' \
+    'graph4=$(git graph --write --update-head --delete-expired) &&
+     test_path_is_file ${packdir}/graph-${graph4}.graph &&
+     test_path_is_file ${packdir}/graph-${graph1}.graph &&
+     test_path_is_file ${packdir}/graph-head &&
+     echo ${graph4} >expect &&
+     cmp -n 40 expect ${packdir}/graph-head &&
+     git graph --read --graph-id=${graph4} >output &&
+     _graph_read_expect "23" "${packdir}" &&
+     cmp expect output'
+
 test_expect_success 'clear graph' \
     'git graph --clear &&
-     test_path_is_missing ${packdir}/graph-${graph2}.graph &&
+     test_path_is_missing ${packdir}/graph-${graph3}.graph &&
+     test_path_is_file ${packdir}/graph-${graph1}.graph &&
      test_path_is_missing ${packdir}/graph-head'
 
 test_expect_success 'setup bare repo' \
@@ -100,7 +133,7 @@ test_expect_success 'write graph in bare repo' \
      echo ${graphbare} >expect &&
      cmp -n 40 expect ${baredir}/graph-head &&
      git graph --read --graph-id=${graphbare} >output &&
-     _graph_read_expect "18" "${baredir}" &&
+     _graph_read_expect "23" "${baredir}" &&
      cmp expect output'
 
 test_done
-- 
2.16.0