On 14-10-14 03:57 PM, Junio C Hamano wrote:
> While use of the --reference option to borrow objects from an
> existing local repository of the same project is an effective way to
> reduce traffic when cloning a project over the network, it makes the
> resulting "borrowing" repository dependent on the "borrowed"
> repository. After running
>
> git clone --reference=P $URL Q
>
> the resulting repository Q will be broken if the borrowed repository
> P disappears.
>
> The way to allow the borrowed repository to be removed is to repack
> the borrowing repository (i.e. run "git repack -a -d" in Q); while
> power users may know it very well, it is not easily discoverable.
>
> Teach a new "--dissociate" option to "git clone" to run this
> repacking for the user.
After reading the above I thought the option would be better named
"--derference". It seemed to me to be something one would like to run after
the first --reference clone.
Looking more closely I see that's not the case. In fact, the option only
makes sense if --reference is also used.
I think things would be more understandable if the option was "--dissociate
<repository>" and was an explicit alternative to --reference:
[[--reference | --dissociate] <repository>]
I'm still not liking the name "--dissociate" though. The original suggestion
of "--borrow" is better. Perhaps "--library" or "--local-cache"? I dunno...
So now I'm wondering if the implementation would be more efficient as an
extension of the --local operation. That is, instead of a post-clone repack,
do a --local clone first followed by a simple "git fetch" from the source repo.
M.
> Signed-off-by: Junio C Hamano <gits...@pobox.com>
> ---
>
> * This comes from
> http://thread.gmane.org/gmane.comp.version-control.git/243918/focus=245397
> which is one of the low-hanging entries in the leftover-bits list
> http://git-blame.blogspot.com/p/leftover-bits.html
>
> Yes, I must have been really bored to do this ;-)
>
> Documentation/git-clone.txt | 11 +++++++++--
> builtin/clone.c | 25 +++++++++++++++++++++++++
> t/t5700-clone-reference.sh | 17 +++++++++++++++++
> 3 files changed, 51 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
> index 0363d00..f1f2a3f 100644
> --- a/Documentation/git-clone.txt
> +++ b/Documentation/git-clone.txt
> @@ -12,7 +12,7 @@ SYNOPSIS
> 'git clone' [--template=<template_directory>]
> [-l] [-s] [--no-hardlinks] [-q] [-n] [--bare] [--mirror]
> [-o <name>] [-b <name>] [-u <upload-pack>] [--reference <repository>]
> - [--separate-git-dir <git dir>]
> + [--dissociate] [--separate-git-dir <git dir>]
> [--depth <depth>] [--[no-]single-branch]
> [--recursive | --recurse-submodules] [--] <repository>
> [<directory>]
> @@ -98,7 +98,14 @@ objects from the source repository into a pack in the
> cloned repository.
> require fewer objects to be copied from the repository
> being cloned, reducing network and local storage costs.
> +
> -*NOTE*: see the NOTE for the `--shared` option.
> +*NOTE*: see the NOTE for the `--shared` option, and also the
> +`--dissociate` option.
> +
> +--dissociate::
> + Borrow the objects from reference repositories specified
> + with the `--reference` options only to reduce network
> + transfer and stop borrowing from them after a clone is made
> + by making necessary local copies of borrowed objects.
>
> --quiet::
> -q::
> diff --git a/builtin/clone.c b/builtin/clone.c
> index bbd169c..780fbd5 100644
> --- a/builtin/clone.c
> +++ b/builtin/clone.c
> @@ -48,6 +48,7 @@ static int option_verbosity;
> static int option_progress = -1;
> static struct string_list option_config;
> static struct string_list option_reference;
> +static int option_dissociate;
>
> static int opt_parse_reference(const struct option *opt, const char *arg,
> int unset)
> {
> @@ -93,6 +94,8 @@ static struct option builtin_clone_options[] = {
> N_("create a shallow clone of that depth")),
> OPT_BOOL(0, "single-branch", &option_single_branch,
> N_("clone only one branch, HEAD or --branch")),
> + OPT_BOOL(0, "dissociate", &option_dissociate,
> + N_("use --reference only while cloning")),
> OPT_STRING(0, "separate-git-dir", &real_git_dir, N_("gitdir"),
> N_("separate git dir from working tree")),
> OPT_STRING_LIST('c', "config", &option_config, N_("key=value"),
> @@ -736,6 +739,21 @@ static void write_refspec_config(const char*
> src_ref_prefix,
> strbuf_release(&value);
> }
>
> +static void dissociate_from_references(void)
> +{
> + struct child_process cmd;
> +
> + memset(&cmd, 0, sizeof(cmd));
> + argv_array_pushl(&cmd.args, "repack", "-a", "-d", NULL);
> + cmd.git_cmd = 1;
> + cmd.out = -1;
> + cmd.no_stdin = 1;
> + if (run_command(&cmd))
> + die(_("cannot repack to clean up"));
> + if (unlink(git_path("objects/info/alternates")) && errno != ENOENT)
> + die_errno(_("cannot unlink temporary alternates file"));
> +}
> +
> int cmd_clone(int argc, const char **argv, const char *prefix)
> {
> int is_bundle = 0, is_local;
> @@ -883,6 +901,10 @@ 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);
> @@ -996,6 +1018,9 @@ int cmd_clone(int argc, const char **argv, const char
> *prefix)
> transport_unlock_pack(transport);
> transport_disconnect(transport);
>
> + if (option_dissociate)
> + dissociate_from_references();
> +
> junk_mode = JUNK_LEAVE_REPO;
> err = checkout();
>
> diff --git a/t/t5700-clone-reference.sh b/t/t5700-clone-reference.sh
> index 6537911..3e783fc 100755
> --- a/t/t5700-clone-reference.sh
> +++ b/t/t5700-clone-reference.sh
> @@ -198,4 +198,21 @@ test_expect_success 'clone using repo pointed at by
> gitfile as reference' '
> test_cmp expected "$base_dir/O/.git/objects/info/alternates"
> '
>
> +test_expect_success 'clone and dissociate from reference' '
> + git init P &&
> + (
> + cd P && test_commit one
> + ) &&
> + git clone P Q &&
> + (
> + cd Q && test_commit two
> + ) &&
> + git clone --no-local --reference=P Q R &&
> + git clone --no-local --reference=P --dissociate Q S &&
> + # removing the reference P would corrupt R but not S
> + rm -fr P &&
> + test_must_fail git -C R fsck &&
> + git -C S fsck
> +'
> +
> test_done
>
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