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[PATCH 08/14] graph: implement git-graph --update-head

From
Derrick Stolee <stolee@gmail.com>
Date
Jan 25, 2018, 14:02 UTC
Message-ID
<20180125140231.65604-9-dstolee@microsoft.com>
In-Reply-To
<20180125140231.65604-1-dstolee@microsoft.com>

It is possible to have multiple packed graph files in a pack directory, but only one is important at a time. Use a 'graph_head' file to point to the important file. Teach git-graph to write 'graph_head' upon writing a new packed graph file.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 Documentation/git-graph.txt | 38 ++++++++++++++++++++++++++++++++++++--
 builtin/graph.c             | 38 +++++++++++++++++++++++++++++++++++---
 packed-graph.c              | 25 +++++++++++++++++++++++++
 packed-graph.h              |  1 +
 t/t5319-graph.sh            | 12 ++++++++++--
 5 files changed, 107 insertions(+), 7 deletions(-)
diff --git a/Documentation/git-graph.txt b/Documentation/git-graph.txt
index 0939c3f1be..ac20aa67a9 100644
--- a/Documentation/git-graph.txt
+++ b/Documentation/git-graph.txt
@@ -12,19 +12,53 @@ SYNOPSIS
 'git graph' --write <options> [--pack-dir <pack_dir>]
 'git graph' --read <options> [--pack-dir <pack_dir>]
 
+OPTIONS
+-------
+--pack-dir::
+	Use given directory for the location of packfiles, graph-head,
+	and graph files.
+
+--read::
+	Read a graph file given by the graph-head file and output basic
+	details about the graph file. (Cannot be combined with --write.)
+
+--graph-id::
+	When used with --read, consider the graph file graph-<oid>.graph.
+
+--write::
+	Write a new graph file to the pack directory. (Cannot be combined
+	with --read.)
+
+--update-head::
+	When used with --write, update the graph-head file to point to
+	the written graph file.
+
 EXAMPLES
 --------
 
+* Output the OID of the graph file pointed to by <dir>/graph-head.
++
+------------------------------------------------
+$ git graph --pack-dir=<dir>
+------------------------------------------------
+
 * Write a graph file for the packed commits in your local .git folder.
 +
 ------------------------------------------------
-$ git midx --write
+$ git graph --write
+------------------------------------------------
+
+* Write a graph file for the packed commits in your local .git folder,
+* and update graph-head.
++
+------------------------------------------------
+$ git graph --write --update-head
 ------------------------------------------------
 
 * Read basic information from a graph file.
 +
 ------------------------------------------------
-$ git midx --read --graph-id=<oid>
+$ git graph --read --graph-id=<oid>
 ------------------------------------------------
 
 CONFIGURATION
diff --git a/builtin/graph.c b/builtin/graph.c
index bc66722924..0760d99f43 100644
--- a/builtin/graph.c
+++ b/builtin/graph.c
@@ -11,7 +11,7 @@
 static char const * const builtin_graph_usage[] ={
 	N_("git graph [--pack-dir <packdir>]"),
 	N_("git graph --read [--graph-id=<oid>]"),
-	N_("git graph --write [--pack-dir <packdir>]"),
+	N_("git graph --write [--pack-dir <packdir>] [--update-head]"),
 	NULL
 };
 
@@ -20,6 +20,9 @@ static struct opts_graph {
 	int read;
 	const char *graph_id;
 	int write;
+	int update_head;
+	int has_existing;
+	struct object_id old_graph_oid;
 } opts;
 
 static int graph_read(void)
@@ -30,8 +33,8 @@ static int graph_read(void)
 
 	if (opts.graph_id && strlen(opts.graph_id) == GIT_MAX_HEXSZ)
 		get_oid_hex(opts.graph_id, &graph_oid);
-	else
-		die("no graph id specified");
+	else if (!get_graph_head_oid(opts.pack_dir, &graph_oid))
+		die("no graph-head exists.");
 
 	graph_file = get_graph_filename_oid(opts.pack_dir, &graph_oid);
 	graph = load_packed_graph_one(graph_file, opts.pack_dir);
@@ -62,10 +65,33 @@ static int graph_read(void)
 	return 0;
 }
 
+static void update_head_file(const char *pack_dir, const struct object_id *graph_id)
+{
+	struct strbuf head_path = STRBUF_INIT;
+	int fd;
+	struct lock_file lk = LOCK_INIT;
+
+	strbuf_addstr(&head_path, pack_dir);
+	strbuf_addstr(&head_path, "/");
+	strbuf_addstr(&head_path, "graph-head");
+
+	fd = hold_lock_file_for_update(&lk, head_path.buf, LOCK_DIE_ON_ERROR);
+	strbuf_release(&head_path);
+
+	if (fd < 0)
+		die_errno("unable to open graph-head");
+
+	write_in_full(fd, oid_to_hex(graph_id), GIT_MAX_HEXSZ);
+	commit_lock_file(&lk);
+}
+
 static int graph_write(void)
 {
 	struct object_id *graph_id = construct_graph(opts.pack_dir);
 
+	if (opts.update_head)
+		update_head_file(opts.pack_dir, graph_id);
+
 	if (graph_id)
 		printf("%s\n", oid_to_hex(graph_id));
 
@@ -83,6 +109,8 @@ int cmd_graph(int argc, const char **argv, const char *prefix)
 			N_("read graph file")),
 		OPT_BOOL('w', "write", &opts.write,
 			N_("write graph file")),
+		OPT_BOOL('u', "update-head", &opts.update_head,
+			N_("update graph-head to written graph file")),
 		{ OPTION_STRING, 'M', "graph-id", &opts.graph_id,
 			N_("oid"),
 			N_("An OID for a specific graph file in the pack-dir."),
@@ -111,11 +139,15 @@ int cmd_graph(int argc, const char **argv, const char *prefix)
 		opts.pack_dir = strbuf_detach(&path, NULL);
 	}
 
+	opts.has_existing = !!get_graph_head_oid(opts.pack_dir, &opts.old_graph_oid);
+
 	if (opts.read)
 		return graph_read();
 	if (opts.write)
 		return graph_write();
 
+	if (opts.has_existing)
+		printf("%s\n", oid_to_hex(&opts.old_graph_oid));
 	return 0;
 }
 
diff --git a/packed-graph.c b/packed-graph.c
index eaa656becb..5723f163ae 100644
--- a/packed-graph.c
+++ b/packed-graph.c
@@ -35,6 +35,31 @@
 #define GRAPH_MIN_SIZE (GRAPH_CHUNKLOOKUP_SIZE + GRAPH_FANOUT_SIZE + \
 			GRAPH_OID_LEN + sizeof(struct packed_graph_header))
 
+struct object_id *get_graph_head_oid(const char *pack_dir, struct object_id *oid)
+{
+	struct strbuf head_filename = STRBUF_INIT;
+	char oid_hex[GIT_MAX_HEXSZ + 1];
+	FILE *f;
+
+	strbuf_addstr(&head_filename, pack_dir);
+	strbuf_addstr(&head_filename, "/graph-head");
+
+	f = fopen(head_filename.buf, "r");
+	strbuf_release(&head_filename);
+
+	if (!f)
+		return 0;
+
+	if (!fgets(oid_hex, sizeof(oid_hex), f))
+		die("failed to read graph-head");
+
+	fclose(f);
+
+	if (get_oid_hex(oid_hex, oid))
+		return 0;
+	return oid;
+}
+
 char* get_graph_filename_oid(const char *pack_dir,
 				  struct object_id *oid)
 {
diff --git a/packed-graph.h b/packed-graph.h
index 1a7eaa2a46..ad561863c8 100644
--- a/packed-graph.h
+++ b/packed-graph.h
@@ -4,6 +4,7 @@
 #include "git-compat-util.h"
 #include "commit.h"
 
+extern struct object_id *get_graph_head_oid(const char *pack_dir, struct object_id *oid);
 extern char* get_graph_filename_oid(const char *pack_dir,
 				    struct object_id *oid);
 
diff --git a/t/t5319-graph.sh b/t/t5319-graph.sh
index 4975f65dee..3919a3ad73 100755
--- a/t/t5319-graph.sh
+++ b/t/t5319-graph.sh
@@ -13,7 +13,8 @@ test_expect_success 'setup full repo' \
      packdir=".git/objects/pack"'
 
 test_expect_success 'write graph with no packs' \
-    'git graph --write --pack-dir .'
+    'git graph --write --pack-dir . &&
+     test_path_is_missing graph-head'
 
 test_expect_success 'create commits and repack' \
     'for i in $(test_seq 5)
@@ -37,6 +38,7 @@ EOF
 test_expect_success 'write graph' \
     'graph1=$(git graph --write) &&
      test_path_is_file ${packdir}/graph-${graph1}.graph &&
+     test_path_is_missing ${packdir}/graph-head &&
      git graph --read --graph-id=${graph1} >output &&
      _graph_read_expect "5" "${packdir}" &&
      cmp expect output'
@@ -69,8 +71,11 @@ test_expect_success 'Add more commits' \
      git repack'
 
 test_expect_success 'write graph with merges' \
-    'graph2=$(git graph --write) &&
+    'graph2=$(git graph --write --update-head) &&
      test_path_is_file ${packdir}/graph-${graph2}.graph &&
+     test_path_is_file ${packdir}/graph-head &&
+     echo ${graph2} >expect &&
+     cmp -n 40 expect ${packdir}/graph-head &&
      git graph --read --graph-id=${graph2} >output &&
      _graph_read_expect "18" "${packdir}" &&
      cmp expect output'
@@ -86,6 +91,9 @@ test_expect_success 'setup bare repo' \
 test_expect_success 'write graph in bare repo' \
     'graphbare=$(git graph --write) &&
      test_path_is_file ${baredir}/graph-${graphbare}.graph &&
+     test_path_is_file ${baredir}/graph-head &&
+     echo ${graphbare} >expect &&
+     cmp -n 40 expect ${baredir}/graph-head &&
      git graph --read --graph-id=${graphbare} >output &&
      _graph_read_expect "18" "${baredir}" &&
      cmp expect output'

-- 
2.16.0
Previous: Derrick StoleeNext: Derrick Stolee
Message 39 of 49 in “Serialized Commit Graph”
  1. 00/14 Serialized Commit GraphDerrick Stolee, Jan 25, 2018
  2. 01/14 graph: add packed graph design documentDerrick Stolee, Jan 25, 2018
  3. Stefan BellerJan 25, 2018
  4. Derrick StoleeJan 26, 2018
  5. Stefan BellerJan 26, 2018
  6. Junio C HamanoJan 25, 2018
  7. Derrick StoleeJan 26, 2018
  8. Duy NguyenJan 26, 2018
  9. 03/14 packed-graph: create git-graph builtinDerrick Stolee, Jan 25, 2018
  10. Stefan BellerJan 25, 2018
  11. Derrick StoleeJan 26, 2018
  12. Junio C HamanoJan 25, 2018
  13. Derrick StoleeJan 26, 2018
  14. Duy NguyenJan 26, 2018
  15. 02/14 packed-graph: add core.graph settingDerrick Stolee, Jan 25, 2018
  16. Stefan BellerJan 25, 2018
  17. Derrick StoleeJan 25, 2018
  18. Junio C HamanoJan 25, 2018
  19. Derrick StoleeJan 26, 2018
  20. 04/14 packed-graph: add format documentDerrick Stolee, Jan 25, 2018
  21. Junio C HamanoJan 25, 2018
  22. Stefan BellerJan 25, 2018
  23. Junio C HamanoJan 25, 2018
  24. Derrick StoleeJan 26, 2018
  25. Stefan BellerJan 25, 2018
  26. Derrick StoleeJan 26, 2018
  27. 09/14 packed-graph: implement git-graph --clearDerrick Stolee, Jan 25, 2018
  28. Stefan BellerJan 25, 2018
  29. 05/14 packed-graph: implement construct_graph()Derrick Stolee, Jan 25, 2018
  30. Stefan BellerJan 25, 2018
  31. Junio C HamanoJan 26, 2018
  32. Junio C HamanoJan 26, 2018
  33. Andreas SchwabJan 26, 2018
  34. Junio C HamanoJan 26, 2018
  35. 06/14 packed-graph: implement git-graph --writeDerrick Stolee, Jan 25, 2018
  36. Stefan BellerJan 25, 2018
  37. Derrick StoleeJan 26, 2018
  38. 14/14 packed-graph: teach git-graph to read commitsDerrick Stolee, Jan 25, 2018
  39. 08/14 graph: implement git-graph --update-headDerrick Stolee, Jan 25, 2018
  40. 07/14 packed-graph: implement git-graph --readDerrick Stolee, Jan 25, 2018
  41. 10/14 packed-graph: teach git-graph --delete-expiredDerrick Stolee, Jan 25, 2018
  42. 12/14 packed-graph: read only from specific pack-indexesDerrick Stolee, Jan 25, 2018
  43. 13/14 packed-graph: close under reachabilityDerrick Stolee, Jan 25, 2018
  44. 11/14 commit: integrate packed graph with commit parsingDerrick Stolee, Jan 25, 2018
  45. Stefan BellerJan 26, 2018
  46. Ævar Arnfjörð BjarmasonJan 25, 2018
  47. Derrick StoleeJan 25, 2018
  48. Ævar Arnfjörð BjarmasonJan 25, 2018
  49. Derrick StoleeJan 26, 2018

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