From: Jeff King <p...@peff.net>

Signed-off-by: Christian Couder <chrisc...@tuxfamily.org>
---
 Makefile                |   2 +
 cache.h                 |   9 ++
 external-odb.c          | 115 +++++++++++++++++++++++
 external-odb.h          |   8 ++
 odb-helper.c            | 239 ++++++++++++++++++++++++++++++++++++++++++++++++
 odb-helper.h            |  25 +++++
 sha1_file.c             |  64 ++++++++++---
 t/t0400-external-odb.sh |  48 ++++++++++
 8 files changed, 495 insertions(+), 15 deletions(-)
 create mode 100644 external-odb.c
 create mode 100644 external-odb.h
 create mode 100644 odb-helper.c
 create mode 100644 odb-helper.h
 create mode 100755 t/t0400-external-odb.sh

diff --git a/Makefile b/Makefile
index de5a030..8641318 100644
--- a/Makefile
+++ b/Makefile
@@ -726,6 +726,7 @@ LIB_OBJS += ewah/ewah_bitmap.o
 LIB_OBJS += ewah/ewah_io.o
 LIB_OBJS += ewah/ewah_rlw.o
 LIB_OBJS += exec_cmd.o
+LIB_OBJS += external-odb.o
 LIB_OBJS += fetch-pack.o
 LIB_OBJS += fsck.o
 LIB_OBJS += gettext.o
@@ -757,6 +758,7 @@ 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 += pack-bitmap.o
 LIB_OBJS += pack-bitmap-write.o
 LIB_OBJS += pack-check.o
diff --git a/cache.h b/cache.h
index 6049f86..cc0a934 100644
--- a/cache.h
+++ b/cache.h
@@ -864,6 +864,12 @@ const char *git_path_shallow(void);
  */
 extern const char *sha1_file_name(const unsigned char *sha1);
 
+/*
+ * Like sha1_file_name, but return the filename within a specific alternate
+ * object directory. Shares the same static buffer with sha1_file_name.
+ */
+extern const char *sha1_file_name_alt(const char *objdir, const unsigned char 
*sha1);
+
 /*
  * Return the name of the (local) packfile with the specified sha1 in
  * its name.  The return value is a pointer to memory that is
@@ -1093,6 +1099,8 @@ extern int do_check_packed_object_crc;
 
 extern int check_sha1_signature(const unsigned char *sha1, void *buf, unsigned 
long size, const char *type);
 
+extern int create_object_tmpfile(struct strbuf *tmp, const char *filename);
+extern void close_sha1_file(int fd);
 extern int finalize_object_file(const char *tmpfile, const char *filename);
 
 extern int has_sha1_pack(const unsigned char *sha1);
@@ -1338,6 +1346,7 @@ extern void read_info_alternates(const char * 
relative_base, int depth);
 extern void add_to_alternates_file(const char *reference);
 typedef int alt_odb_fn(struct alternate_object_database *, void *);
 extern int foreach_alt_odb(alt_odb_fn, void*);
+extern void prepare_external_alt_odb(void);
 
 struct pack_window {
        struct pack_window *next;
diff --git a/external-odb.c b/external-odb.c
new file mode 100644
index 0000000..1ccfa99
--- /dev/null
+++ b/external-odb.c
@@ -0,0 +1,115 @@
+#include "cache.h"
+#include "external-odb.h"
+#include "odb-helper.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 int external_odb_config(const char *var, const char *value, void *data)
+{
+       struct odb_helper *o;
+       const char *key, *dot;
+
+       if (!skip_prefix(var, "odb.", &key))
+               return 0;
+       dot = strrchr(key, '.');
+       if (!dot)
+               return 0;
+
+       o = find_or_create_helper(key, dot - key);
+       key = dot + 1;
+
+       if (!strcmp(key, "command"))
+               return git_config_string(&o->cmd, var, value);
+
+       return 0;
+}
+
+static void external_odb_init(void)
+{
+       static int initialized;
+
+       if (initialized)
+               return;
+       initialized = 1;
+
+       git_config(external_odb_config, NULL);
+}
+
+const char *external_odb_root(void)
+{
+       static const char *root;
+       if (!root)
+               root = git_pathdup("objects/external");
+       return root;
+}
+
+int external_odb_has_object(const unsigned char *sha1)
+{
+       struct odb_helper *o;
+
+       external_odb_init();
+
+       for (o = helpers; o; o = o->next)
+               if (odb_helper_has_object(o, sha1))
+                       return 1;
+       return 0;
+}
+
+int external_odb_fetch_object(const unsigned char *sha1)
+{
+       struct odb_helper *o;
+       const char *path;
+
+       if (!external_odb_has_object(sha1))
+               return -1;
+
+       path = sha1_file_name_alt(external_odb_root(), sha1);
+       safe_create_leading_directories_const(path);
+       prepare_external_alt_odb();
+
+       for (o = helpers; o; o = o->next) {
+               struct strbuf tmpfile = STRBUF_INIT;
+               int ret;
+               int fd;
+
+               if (!odb_helper_has_object(o, sha1))
+                       continue;
+
+               fd = create_object_tmpfile(&tmpfile, path);
+               if (fd < 0) {
+                       strbuf_release(&tmpfile);
+                       return -1;
+               }
+
+               if (odb_helper_fetch_object(o, sha1, fd) < 0) {
+                       close(fd);
+                       unlink(tmpfile.buf);
+                       strbuf_release(&tmpfile);
+                       continue;
+               }
+
+               close_sha1_file(fd);
+               ret = finalize_object_file(tmpfile.buf, path);
+               strbuf_release(&tmpfile);
+               if (!ret)
+                       return 0;
+       }
+
+       return -1;
+}
diff --git a/external-odb.h b/external-odb.h
new file mode 100644
index 0000000..2397477
--- /dev/null
+++ b/external-odb.h
@@ -0,0 +1,8 @@
+#ifndef EXTERNAL_ODB_H
+#define EXTERNAL_ODB_H
+
+const char *external_odb_root(void);
+int external_odb_has_object(const unsigned char *sha1);
+int external_odb_fetch_object(const unsigned char *sha1);
+
+#endif /* EXTERNAL_ODB_H */
diff --git a/odb-helper.c b/odb-helper.c
new file mode 100644
index 0000000..7029a59
--- /dev/null
+++ b/odb-helper.c
@@ -0,0 +1,239 @@
+#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;
+}
+
+struct odb_helper_cmd {
+       struct argv_array argv;
+       struct child_process child;
+};
+
+static void prepare_helper_command(struct argv_array *argv, const char *cmd,
+                                  const char *fmt, va_list ap)
+{
+       struct strbuf buf = STRBUF_INIT;
+
+       strbuf_addstr(&buf, cmd);
+       strbuf_addch(&buf, ' ');
+       strbuf_vaddf(&buf, fmt, ap);
+
+       argv_array_push(argv, buf.buf);
+       strbuf_release(&buf);
+}
+
+__attribute__((format (printf,3,4)))
+static int odb_helper_start(struct odb_helper *o,
+                           struct odb_helper_cmd *cmd,
+                           const char *fmt, ...)
+{
+       va_list ap;
+
+       memset(cmd, 0, sizeof(*cmd));
+       argv_array_init(&cmd->argv);
+
+       if (!o->cmd)
+               return -1;
+
+       va_start(ap, fmt);
+       prepare_helper_command(&cmd->argv, o->cmd, fmt, ap);
+       va_end(ap);
+
+       cmd->child.argv = cmd->argv.argv;
+       cmd->child.use_shell = 1;
+       cmd->child.no_stdin = 1;
+       cmd->child.out = -1;
+
+       if (start_command(&cmd->child) < 0) {
+               argv_array_clear(&cmd->argv);
+               return -1;
+       }
+
+       return 0;
+}
+
+static int odb_helper_finish(struct odb_helper *o,
+                            struct odb_helper_cmd *cmd)
+{
+       int ret = finish_command(&cmd->child);
+       argv_array_clear(&cmd->argv);
+       if (ret) {
+               warning("odb helper '%s' reported failure", o->name);
+               return -1;
+       }
+       return 0;
+}
+
+static int parse_object_line(struct odb_helper_object *o, const char *line)
+{
+       char *end;
+       if (get_sha1_hex(line, o->sha1) < 0)
+               return -1;
+
+       line += 40;
+       if (*line++ != ' ')
+               return -1;
+
+       o->size = strtoul(line, &end, 10);
+       if (line == end || *end++ != ' ')
+               return -1;
+
+       o->type = type_from_string(end);
+       return 0;
+}
+
+static int odb_helper_object_cmp(const void *va, const void *vb)
+{
+       const struct odb_helper_object *a = va, *b = vb;
+       return hashcmp(a->sha1, b->sha1);
+}
+
+static void odb_helper_load_have(struct odb_helper *o)
+{
+       struct odb_helper_cmd cmd;
+       FILE *fh;
+       struct strbuf line = STRBUF_INIT;
+
+       if (o->have_valid)
+               return;
+       o->have_valid = 1;
+
+       if (odb_helper_start(o, &cmd, "have") < 0)
+               return;
+
+       fh = xfdopen(cmd.child.out, "r");
+       while (strbuf_getline(&line, fh) != EOF) {
+               ALLOC_GROW(o->have, o->have_nr+1, o->have_alloc);
+               if (parse_object_line(&o->have[o->have_nr], line.buf) < 0) {
+                       warning("bad 'have' input from odb helper '%s': %s",
+                               o->name, line.buf);
+                       break;
+               }
+               o->have_nr++;
+       }
+
+       strbuf_release(&line);
+       fclose(fh);
+       odb_helper_finish(o, &cmd);
+
+       qsort(o->have, o->have_nr, sizeof(*o->have), odb_helper_object_cmp);
+}
+
+static struct odb_helper_object *odb_helper_lookup(struct odb_helper *o,
+                                                  const unsigned char *sha1)
+{
+       int idx;
+
+       odb_helper_load_have(o);
+       idx = sha1_entry_pos(o->have, sizeof(*o->have), 0,
+                            0, o->have_nr, o->have_nr,
+                            sha1);
+       if (idx < 0)
+               return NULL;
+       return &o->have[idx];
+}
+
+int odb_helper_has_object(struct odb_helper *o, const unsigned char *sha1)
+{
+       return !!odb_helper_lookup(o, sha1);
+}
+
+int odb_helper_fetch_object(struct odb_helper *o, const unsigned char *sha1,
+                           int fd)
+{
+       struct odb_helper_object *obj;
+       struct odb_helper_cmd cmd;
+       unsigned long total_got;
+       git_zstream stream;
+       int zret;
+       git_SHA_CTX hash;
+       unsigned char real_sha1[20];
+
+       obj = odb_helper_lookup(o, sha1);
+       if (!obj)
+               return -1;
+
+       if (odb_helper_start(o, &cmd, "get %s", sha1_to_hex(sha1)) < 0)
+               return -1;
+
+       memset(&stream, 0, sizeof(stream));
+       git_inflate_init(&stream);
+       git_SHA1_Init(&hash);
+       total_got = 0;
+
+       for (;;) {
+               unsigned char buf[4096];
+               int r;
+
+               r = xread(cmd.child.out, buf, sizeof(buf));
+               if (r < 0) {
+                       error("unable to read from odb helper '%s': %s",
+                             o->name, strerror(errno));
+                       close(cmd.child.out);
+                       odb_helper_finish(o, &cmd);
+                       git_inflate_end(&stream);
+                       return -1;
+               }
+               if (r == 0)
+                       break;
+
+               write_or_die(fd, buf, r);
+
+               stream.next_in = buf;
+               stream.avail_in = r;
+               do {
+                       unsigned char inflated[4096];
+                       unsigned long got;
+
+                       stream.next_out = inflated;
+                       stream.avail_out = sizeof(inflated);
+                       zret = git_inflate(&stream, Z_SYNC_FLUSH);
+                       got = sizeof(inflated) - stream.avail_out;
+
+                       git_SHA1_Update(&hash, inflated, got);
+                       /* skip header when counting size */
+                       if (!total_got) {
+                               const unsigned char *p = memchr(inflated, '\0', 
got);
+                               if (p)
+                                       got -= p - inflated + 1;
+                               else
+                                       got = 0;
+                       }
+                       total_got += got;
+               } while (stream.avail_in && zret == Z_OK);
+       }
+
+       close(cmd.child.out);
+       git_inflate_end(&stream);
+       git_SHA1_Final(real_sha1, &hash);
+       if (odb_helper_finish(o, &cmd))
+               return -1;
+       if (zret != Z_STREAM_END) {
+               warning("bad zlib data from odb helper '%s' for %s",
+                       o->name, sha1_to_hex(sha1));
+               return -1;
+       }
+       if (total_got != obj->size) {
+               warning("size mismatch from odb helper '%s' for %s (%lu != 
%lu)",
+                       o->name, sha1_to_hex(sha1), total_got, obj->size);
+               return -1;
+       }
+       if (hashcmp(real_sha1, sha1)) {
+               warning("sha1 mismatch from odb helper '%s' for %s (got %s)",
+                       o->name, sha1_to_hex(sha1), sha1_to_hex(real_sha1));
+               return -1;
+       }
+
+       return 0;
+}
diff --git a/odb-helper.h b/odb-helper.h
new file mode 100644
index 0000000..0f704f9
--- /dev/null
+++ b/odb-helper.h
@@ -0,0 +1,25 @@
+#ifndef ODB_HELPER_H
+#define ODB_HELPER_H
+
+struct odb_helper {
+       const char *name;
+       const char *cmd;
+
+       struct odb_helper_object {
+               unsigned char sha1[20];
+               unsigned long size;
+               enum object_type type;
+       } *have;
+       int have_nr;
+       int have_alloc;
+       int have_valid;
+
+       struct odb_helper *next;
+};
+
+struct odb_helper *odb_helper_new(const char *name, int namelen);
+int odb_helper_has_object(struct odb_helper *o, const unsigned char *sha1);
+int odb_helper_fetch_object(struct odb_helper *o, const unsigned char *sha1,
+                           int fd);
+
+#endif /* ODB_HELPER_H */
diff --git a/sha1_file.c b/sha1_file.c
index d5e1121..a707bc1 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -23,6 +23,7 @@
 #include "bulk-checkin.h"
 #include "streaming.h"
 #include "dir.h"
+#include "external-odb.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -183,13 +184,11 @@ static void fill_sha1_path(char *pathbuf, const unsigned 
char *sha1)
        }
 }
 
-const char *sha1_file_name(const unsigned char *sha1)
+const char *sha1_file_name_alt(const char *objdir, const unsigned char *sha1)
 {
        static char buf[PATH_MAX];
-       const char *objdir;
        int len;
 
-       objdir = get_object_directory();
        len = strlen(objdir);
 
        /* '/' + sha1(2) + '/' + sha1(38) + '\0' */
@@ -203,6 +202,11 @@ const char *sha1_file_name(const unsigned char *sha1)
        return buf;
 }
 
+const char *sha1_file_name(const unsigned char *sha1)
+{
+       return sha1_file_name_alt(get_object_directory(), sha1);
+}
+
 /*
  * Return the name of the pack or index file with the specified sha1
  * in its filename.  *base and *name are scratch space that must be
@@ -439,6 +443,21 @@ int foreach_alt_odb(alt_odb_fn fn, void *cb)
        return r;
 }
 
+void prepare_external_alt_odb(void)
+{
+       static int linked_external;
+       const char *path;
+
+       if (linked_external)
+               return;
+
+       path = external_odb_root();
+       if (!access(path, F_OK)) {
+               link_alt_odb_entry(path, NULL, 0, "");
+               linked_external = 1;
+       }
+}
+
 void prepare_alt_odb(void)
 {
        const char *alt;
@@ -453,6 +472,7 @@ void prepare_alt_odb(void)
        link_alt_odb_entries(alt, strlen(alt), PATH_SEP, NULL, 0);
 
        read_info_alternates(get_object_directory(), 0);
+       prepare_external_alt_odb();
 }
 
 /* Returns 1 if we have successfully freshened the file, 0 otherwise. */
@@ -493,7 +513,7 @@ static int check_and_freshen_nonlocal(const unsigned char 
*sha1, int freshen)
                if (check_and_freshen_file(alt->base, freshen))
                        return 1;
        }
-       return 0;
+       return external_odb_has_object(sha1);
 }
 
 static int check_and_freshen(const unsigned char *sha1, int freshen)
@@ -1523,19 +1543,15 @@ static int stat_sha1_file(const unsigned char *sha1, 
struct stat *st)
        return -1;
 }
 
-static int open_sha1_file(const unsigned char *sha1)
+static int open_sha1_file_alt(const unsigned char *sha1)
 {
-       int fd;
        struct alternate_object_database *alt;
-       int most_interesting_errno;
-
-       fd = git_open_noatime(sha1_file_name(sha1));
-       if (fd >= 0)
-               return fd;
-       most_interesting_errno = errno;
+       int most_interesting_errno = errno;
 
        prepare_alt_odb();
        for (alt = alt_odb_list; alt; alt = alt->next) {
+               int fd;
+
                fill_sha1_path(alt->name, sha1);
                fd = git_open_noatime(alt->base);
                if (fd >= 0)
@@ -1547,6 +1563,24 @@ static int open_sha1_file(const unsigned char *sha1)
        return -1;
 }
 
+static int open_sha1_file(const unsigned char *sha1)
+{
+       int fd;
+
+       fd = git_open_noatime(sha1_file_name(sha1));
+       if (fd >= 0)
+               return fd;
+
+       fd = open_sha1_file_alt(sha1);
+       if (fd >= 0)
+               return fd;
+
+       if (!external_odb_fetch_object(sha1))
+               fd = open_sha1_file_alt(sha1);
+
+       return fd;
+}
+
 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 {
        void *map;
@@ -3011,7 +3045,7 @@ int hash_sha1_file(const void *buf, unsigned long len, 
const char *type,
 }
 
 /* Finalize a file on disk, and close it. */
-static void close_sha1_file(int fd)
+void close_sha1_file(int fd)
 {
        if (fsync_object_files)
                fsync_or_die(fd, "sha1 file");
@@ -3035,7 +3069,7 @@ static inline int directory_size(const char *filename)
  * We want to avoid cross-directory filename renames, because those
  * can have problems on various filesystems (FAT, NFS, Coda).
  */
-static int create_tmpfile(struct strbuf *tmp, const char *filename)
+int create_object_tmpfile(struct strbuf *tmp, const char *filename)
 {
        int fd, dirlen = directory_size(filename);
 
@@ -3075,7 +3109,7 @@ static int write_loose_object(const unsigned char *sha1, 
char *hdr, int hdrlen,
        static struct strbuf tmp_file = STRBUF_INIT;
        const char *filename = sha1_file_name(sha1);
 
-       fd = create_tmpfile(&tmp_file, filename);
+       fd = create_object_tmpfile(&tmp_file, filename);
        if (fd < 0) {
                if (errno == EACCES)
                        return error("insufficient permission for adding an 
object to repository database %s", get_object_directory());
diff --git a/t/t0400-external-odb.sh b/t/t0400-external-odb.sh
new file mode 100755
index 0000000..2b01617
--- /dev/null
+++ b/t/t0400-external-odb.sh
@@ -0,0 +1,48 @@
+#!/bin/sh
+
+test_description='basic tests for external object databases'
+
+. ./test-lib.sh
+
+ALT_SOURCE="$PWD/alt-repo/.git"
+export ALT_SOURCE
+write_script odb-helper <<\EOF
+GIT_DIR=$ALT_SOURCE; export GIT_DIR
+case "$1" in
+have)
+       git rev-list --all --objects |
+       cut -d' ' -f1 |
+       git cat-file --batch-check |
+       awk '{print $1 " " $3 " " $2}'
+       ;;
+get)
+       cat "$GIT_DIR"/objects/$(echo $2 | sed 's#..#&/#')
+       ;;
+esac
+EOF
+HELPER="\"$PWD\"/odb-helper"
+
+test_expect_success 'setup alternate repo' '
+       git init alt-repo &&
+       (cd alt-repo &&
+        test_commit one &&
+        test_commit two
+       ) &&
+       alt_head=`cd alt-repo && git rev-parse HEAD`
+'
+
+test_expect_success 'alt objects are missing' '
+       test_must_fail git log --format=%s $alt_head
+'
+
+test_expect_success 'helper can retrieve alt objects' '
+       test_config odb.magic.command "$HELPER" &&
+       cat >expect <<-\EOF &&
+       two
+       one
+       EOF
+       git log --format=%s $alt_head >actual &&
+       test_cmp expect actual
+'
+
+test_done
-- 
2.9.0.rc2.362.g3cd93d0

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