[GSoC PATCH 0/3] preserve promisor files content after repack

The goal of this patch is to solve the NEEDSWORK comment added by 5374a290 (fetch-pack: write fetched refs to .promisor, 14/10/2019). This is done by adding a helper function that takes the content of all .promisor files in the `repository`, and copies it inside the first .promisor file created by the repack.

Also, I added a comment explaining what is the purpose of the content of the .promisor files, since this wasn't explained anywhere (I found information regarding this only in the message of the previously cited commit).

I am not satisfied at all with this patch, and I would love to have some
feedback for the v2. The issues/questions that I had while writing these
patches are the following:
 * Is there a way to not have to check line by line if the content of
   .promisor files are already inside the destination .promisor file?
 * Does it make sense to copy everything inside the first .promisor file
   created by the repack? Is it worth the effort make sure to copy each
   ref (and associatde hash) inside the .promisor file of the packfile
   that contains that ref?

LorenzoPegorari (3):
  pack-write: add explanation to promisor file content
  pack-write: add helper to fill promisor file after repack
  repack-promisor: preserve content of promisor files after repack

 Documentation/git-repack.adoc |  4 +-
 pack-write.c                  | 71 +++++++++++++++++++++++++++++++++++
 pack.h                        |  1 +
 repack-promisor.c             | 23 ++++++++----
 4 files changed, 89 insertions(+), 10 deletions(-)