[PATCH] Use the alternates of the source repository for dissociating clone

[Alexander Riesen <alexander.riesen@cetitec.com>]

The "--dissociate" option required reference repositories, which sometimes
demanded a look into the objects/info/alternates by the user. As this
is something which can be figured out automatically, do it in the
clone unless there is no other reference repositories.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
---

I often (enough) did something like this (preparing for manual backup):

     # Run mc (the Midnight Commander, it is a console (ncurses) file manager with
     # two panels).
     # Select a repository.
     $ git clone --mirror --dissociate \
       $(sed -e 's|\(.*\)/objects|--reference \1| -- 
%f/.git/objects/info/alternates' 2>/dev/null) \
       %f %D/%f
     # (except that this is one long line in mc)

The '%f' expands to a selected directory on the current panel, %D - to the
current directory on the other panel. But as I see, the combination of the
options "--dissociate" and no given references is not used for anything but
giving the warning yet. So maybe it can be used as a shortcut for the above?

  builtin/clone.c | 42 ++++++++++++++++++++++++++++++++++++++----
  1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index 578da85..344bf21 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -791,6 +791,38 @@ static void write_refspec_config(const char *src_ref_prefix,
      strbuf_release(&value);
  }

+static int copy_alternates_to_references(const char *src_repo)
+{
+    int refcnt = -1;
+    char *src_alternates = mkpathdup("%s/objects/info/alternates", src_repo);
+    FILE *in = fopen(src_alternates, "r");
+    if (in) {
+        struct strbuf line = STRBUF_INIT;
+        refcnt = 0;
+        while (strbuf_getline(&line, in, '\n') != EOF) {
+            struct string_list_item item;
+            if (line.len < 8 || line.buf[0] == '#')
+                continue;
+            ++refcnt;
+            if (!strcmp(line.buf + line.len - 8, "/objects"))
+                line.buf[line.len - 8] = '\0';
+            if (is_absolute_path(line.buf)) {
+                item.string = line.buf;
+                add_one_reference(&item, NULL);
+                continue;
+            }
+            item.string = mkpathdup("%s/objects/%s", src_repo, line.buf);
+            normalize_path_copy(item.string, item.string);
+            add_one_reference(&item, NULL);
+            free(item.string);
+        }
+        strbuf_release(&line);
+        fclose(in);
+    }
+    free(src_alternates);
+    return refcnt;
+}
+
  static void dissociate_from_references(void)
  {
      static const char* argv[] = { "repack", "-a", "-d", NULL };
@@ -947,10 +979,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)

      if (option_reference.nr)
          setup_reference();
-    else if (option_dissociate) {
-        warning(_("--dissociate given, but there is no --reference"));
-        option_dissociate = 0;
-    }

      fetch_pattern = value.buf;
      refspec = parse_fetch_refspec(1, &fetch_pattern);
@@ -976,6 +1004,12 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
          warning(_("--local is ignored"));
      transport->cloning = 1;

+    if (!option_reference.nr && option_dissociate &&
+        copy_alternates_to_references(path) <= 0) {
+        warning(_("--dissociate given, but there is no --reference"));
+        option_dissociate = 0;
+    }
+
      if (!transport->get_refs_list || (!is_local && !transport->fetch))
          die(_("Don't know how to clone %s"), transport->url);

-- 
2.6.1.150.gb633014