[PATCH v5 2/8] Add initial remote odb support

[Christian Couder <christian.couder@gmail.com>]

From: Christian Couder <christian.couder@gmail.com>

The remote-odb.{c,h} files will contain the functions
that are called by the rest of Git mostly from
"sha1-file.c" to access the objects managed by the
remote odbs.

The odb-helper.{c,h} files will contain the functions to
actually implement communication with either the internal
functions or the external scripts or processes that will
manage and provide remote git objects.

For now only infrastructure to create helpers from the
config and to check if there are remote odbs and odb
helpers is implemented.

We expect that there will not be a lot of helpers, so it
is ok to use a simple linked list to manage them.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Makefile     |  2 ++
 odb-helper.c | 16 +++++++++
 odb-helper.h | 19 +++++++++++
 remote-odb.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 remote-odb.h |  7 ++++
 5 files changed, 135 insertions(+)
 create mode 100644 odb-helper.c
 create mode 100644 odb-helper.h
 create mode 100644 remote-odb.c
 create mode 100644 remote-odb.h

diff --git a/Makefile b/Makefile
index 13e1c52478..bed0b64ff7 100644
--- a/Makefile
+++ b/Makefile
@@ -915,6 +915,8 @@ LIB_OBJS += notes-cache.o
 LIB_OBJS += notes-merge.o
 LIB_OBJS += notes-utils.o
 LIB_OBJS += object.o
+LIB_OBJS += odb-helper.o
+LIB_OBJS += remote-odb.o
 LIB_OBJS += oidmap.o
 LIB_OBJS += oidset.o
 LIB_OBJS += packfile.o
diff --git a/odb-helper.c b/odb-helper.c
new file mode 100644
index 0000000000..b4d403ffa9
--- /dev/null
+++ b/odb-helper.c
@@ -0,0 +1,16 @@
+#include "cache.h"
+#include "object.h"
+#include "argv-array.h"
+#include "odb-helper.h"
+#include "run-command.h"
+#include "sha1-lookup.h"
+
+struct odb_helper *odb_helper_new(const char *name, int namelen)
+{
+	struct odb_helper *o;
+
+	o = xcalloc(1, sizeof(*o));
+	o->name = xmemdupz(name, namelen);
+
+	return o;
+}
diff --git a/odb-helper.h b/odb-helper.h
new file mode 100644
index 0000000000..4b792a3896
--- /dev/null
+++ b/odb-helper.h
@@ -0,0 +1,19 @@
+#ifndef ODB_HELPER_H
+#define ODB_HELPER_H
+
+/*
+ * An odb helper is a way to access a remote odb.
+ *
+ * Information in its fields comes from the config file [odb "NAME"]
+ * entries.
+ */
+struct odb_helper {
+	const char *name;                 /* odb.<NAME>.* */
+	const char *remote;               /* odb.<NAME>.promisorRemote */
+
+	struct odb_helper *next;
+};
+
+extern struct odb_helper *odb_helper_new(const char *name, int namelen);
+
+#endif /* ODB_HELPER_H */
diff --git a/remote-odb.c b/remote-odb.c
new file mode 100644
index 0000000000..03be54ba2e
--- /dev/null
+++ b/remote-odb.c
@@ -0,0 +1,91 @@
+#include "cache.h"
+#include "remote-odb.h"
+#include "odb-helper.h"
+#include "config.h"
+
+static struct odb_helper *helpers;
+static struct odb_helper **helpers_tail = &helpers;
+
+static struct odb_helper *find_or_create_helper(const char *name, int len)
+{
+	struct odb_helper *o;
+
+	for (o = helpers; o; o = o->next)
+		if (!strncmp(o->name, name, len) && !o->name[len])
+			return o;
+
+	o = odb_helper_new(name, len);
+	*helpers_tail = o;
+	helpers_tail = &o->next;
+
+	return o;
+}
+
+static struct odb_helper *do_find_odb_helper(const char *remote)
+{
+	struct odb_helper *o;
+
+	for (o = helpers; o; o = o->next)
+		if (o->remote && !strcmp(o->remote, remote))
+			return o;
+
+	return NULL;
+}
+
+static int remote_odb_config(const char *var, const char *value, void *data)
+{
+	struct odb_helper *o;
+	const char *name;
+	int namelen;
+	const char *subkey;
+
+	if (parse_config_key(var, "odb", &name, &namelen, &subkey) < 0)
+		return 0;
+
+	o = find_or_create_helper(name, namelen);
+
+	if (!strcmp(subkey, "promisorremote")) {
+		const char *remote;
+		int res = git_config_string(&remote, var, value);
+
+		if (res)
+			return res;
+
+		if (do_find_odb_helper(remote))
+			return error(_("when parsing config key '%s' "
+				       "helper for remote '%s' already exists"),
+				     var, remote);
+
+		o->remote = remote;
+
+		return 0;
+	}
+
+	return 0;
+}
+
+static void remote_odb_init(void)
+{
+	static int initialized;
+
+	if (initialized)
+		return;
+	initialized = 1;
+
+	git_config(remote_odb_config, NULL);
+}
+
+struct odb_helper *find_odb_helper(const char *remote)
+{
+	remote_odb_init();
+
+	if (!remote)
+		return helpers;
+
+	return do_find_odb_helper(remote);
+}
+
+int has_remote_odb(void)
+{
+	return !!find_odb_helper(NULL);
+}
diff --git a/remote-odb.h b/remote-odb.h
new file mode 100644
index 0000000000..4c7b13695f
--- /dev/null
+++ b/remote-odb.h
@@ -0,0 +1,7 @@
+#ifndef REMOTE_ODB_H
+#define REMOTE_ODB_H
+
+extern struct odb_helper *find_odb_helper(const char *remote);
+extern int has_remote_odb(void);
+
+#endif /* REMOTE_ODB_H */
-- 
2.19.0.278.gca5b891cac