[PATCHv4 0/6] git clone: Marry --recursive and --reference

v4: Thanks to Junios critial questions regarding the design, I took a step back to look at the bigger picture, again.

new patches:
  clone: factor out checking for an alternate path
  clone: recursive and reference option triggers submodule alternates
  
The last patch redesigns completely how we approach the problem.
Now there are no new command line options (that relate to the problem
of marrying --recursive and --reference), but instead we communicate
everything via configuration options to have a lasting effect (i.e.
submodule update remembers the decision of the initial setup)

Thanks, Stefan

v3:

Thanks to Junios critial questions regarding the design, I took a step back to look at the bigger picture.

--super-reference sounds confusing. (what is the super referring to?) So drop that approach.

Instead we'll compute where the reference might be in the superproject scope and ask the submodule clone operation to consider an optional reference. If the referenced alternate is not there, we'll just warn about it and carry on.

* fixed the style in patch 2.

* fixed another bug in the last patch, that is unrelated, but would have helped
  me a lot.

Thanks, Stefan

 Documentation/git-clone.txt    |   9 ++++++++-
 builtin/clone.c                |  36 ++++++++++++++++++++++++++++--------
 builtin/submodule--helper.c    | 105 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------
 git-submodule.sh               |   2 +-
 t/t7408-submodule-reference.sh | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------------------------------
 5 files changed, 217 insertions(+), 97 deletions(-)

v2:
 * fixed the p1,2 cleanups
 * added documentation to patches 5,6
 * improved commit message in v4
 
 Thanks,
 Stefan
 
v1:
 
 Currently when cloning a superproject with --recursive and --reference
 only the superproject learns about its alternates. The submodules are
 cloned independently, which may incur lots of network costs.
 
 Assume that the reference repository has the submodules at the same
 paths as the to-be-cloned submodule and try to setup alternates from
 there.
 
 Some submodules in the referenced superproject may not be there, 
 (they are just not initialized/cloned/checked out), which yields
 an error for now. In future work we may want to soften the alternate
 check and not die in the clone when one of the given alternates doesn't
 exist.
 
 patch 1,2 are modernizing style of t7408, 
 patches 3,4 are not strictly necessary, but I think it is a good thing
 to not leave the submodule related C code in a crippled state (i.e.
 allowing only one reference). The shell code would also need this update,
 but it looked ugly to me, so I postpone it until more of the submodule code
 is written in C. 
 
 Thanks,
 Stefan 

Stefan Beller (6):
  t7408: modernize style
  t7408: merge short tests, factor out testing method
  submodule--helper module-clone: allow multiple references
  submodule--helper update-clone: allow multiple references
  submodule update: add super-reference flag
  clone: reference flag is used for submodules as well

 builtin/clone.c                |  22 ++++--
 builtin/submodule--helper.c    |  45 ++++++++----
 git-submodule.sh               |  12 +++-
 t/t7408-submodule-reference.sh | 153 +++++++++++++++++++++++------------------
 4 files changed, 147 insertions(+), 85 deletions(-)