Re: [PATCH] fetch/git: add support for disabling shared clones on unpack

[Henning Schild <henning.schild@siemens.com>]

We actually ran into that issue on a build system called Isar.

https://github.com/ilbers/isar

This build system executes some tasks in a chroot. In this chroot a
"shared" clone will not work because it expects its "alternate" to be
at the very same location it was outside the chroot. We considered
several hacks in Isar
- patching the alternates before and after chroot
- mounting the "alternate" to the exact location in chroot
None of this is really nice, so we decided to try and do something
about it upstream.

regards,
Henning

Am Tue, 12 Dec 2017 15:44:43 +0100
schrieb Henning Schild <henning.schild@siemens.com>:

> By default the unpacker will create a "shared" clone when cloning from
> the DL_DIR to the WORKDIR. This patch introduces an option to control
> that behaviour. Probably something that hardly anyone would want to
> do.
> 
> Imagine some recipe steps are executed in a namespace that is
> different from the one your downloader and unpacker ran in. (chroot)
> Because a "shared" clone has an absolute reference to its "alternate"
> you now have to make that "alternate" visible in that new namespace
> (chroot) at the exact place.
> 
> With this patch you can unpack "noshared" and get a stand-alone copy.
> This copy will also work if the "alternate" is not visible or
> existant.
> 
> Signed-off-by: Henning Schild <henning.schild@siemens.com>
> ---
>  lib/bb/fetch2/git.py | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/bb/fetch2/git.py b/lib/bb/fetch2/git.py
> index 5ef8cd69..30b88c83 100644
> --- a/lib/bb/fetch2/git.py
> +++ b/lib/bb/fetch2/git.py
> @@ -53,6 +53,13 @@ Supported SRC_URI options are:
>     For local git:// urls to use the current branch HEAD as the
> revision for use with AUTOREV. Implies nobranch.
>  
> +- noshared
> +   When unpacking do not clone with the parameter "--shared". This
> option will
> +   allow the unpacked copy to work stand-alone i.e. if your recipe
> runs in a
> +   chroot where the "alternate" can not be found. Setting this will
> increase
> +   the unpack-time and the disk-usage.
> +   The default is "0", set noshared=1 if needed.
> +
>  """
>  
>  #Copyright (C) 2005 Richard Purdie
> @@ -159,6 +166,8 @@ class Git(FetchMethod):
>  
>          ud.nobranch = ud.parm.get("nobranch","0") == "1"
>  
> +        ud.noshared = ud.parm.get("noshared","0") == "1"
> +
>          # usehead implies nobranch
>          ud.usehead = ud.parm.get("usehead","0") == "1"
>          if ud.usehead:
> @@ -176,7 +185,9 @@ class Git(FetchMethod):
>          if len(branches) != len(ud.names):
>              raise bb.fetch2.ParameterError("The number of name and
> branch parameters is not balanced", ud.url) 
> -        ud.cloneflags = "-s -n"
> +        cloneflags = "-n"
> +        if not ud.noshared:
> +            cloneflags += " -s"
>          if ud.bareclone:
>              ud.cloneflags += " --mirror"
>