FM / technical

/usr/share/doc/git/technical

Name	Size	Mode	Actions
api-error-handling.html	22259	0644	edit dl rm
api-error-handling.txt	3818	0644	edit dl rm
api-index-skel.txt	432	0644	edit dl rm
api-index.html	17183	0644	edit dl rm
api-index.sh	611	0644	edit dl rm
api-index.txt	648	0644	edit dl rm
api-merge.html	18305	0644	edit dl rm
api-merge.txt	1090	0644	edit dl rm
api-parse-options.html	36657	0644	edit dl rm
api-parse-options.txt	13157	0644	edit dl rm
api-simple-ipc.html	22388	0644	edit dl rm
api-simple-ipc.txt	4852	0644	edit dl rm
api-trace2.html	77619	0644	edit dl rm
api-trace2.txt	44255	0644	edit dl rm
bitmap-format.html	30403	0644	edit dl rm
bitmap-format.txt	8871	0644	edit dl rm
bundle-uri.html	51387	0644	edit dl rm
bundle-uri.txt	26787	0644	edit dl rm
commit-graph.txt	17957	0644	edit dl rm
directory-rename-detection.txt	5199	0644	edit dl rm
hash-function-transition.html	64539	0644	edit dl rm
hash-function-transition.txt	35894	0644	edit dl rm
long-running-process-protocol.html	18995	0644	edit dl rm
long-running-process-protocol.txt	1929	0644	edit dl rm
multi-pack-index.html	22462	0644	edit dl rm
multi-pack-index.txt	4459	0644	edit dl rm
pack-heuristics.html	43594	0644	edit dl rm
pack-heuristics.txt	18040	0644	edit dl rm
packfile-uri.txt	3748	0644	edit dl rm
parallel-checkout.html	31715	0644	edit dl rm
parallel-checkout.txt	12301	0644	edit dl rm
partial-clone.html	36496	0644	edit dl rm
partial-clone.txt	14968	0644	edit dl rm
racy-git.html	27995	0644	edit dl rm
racy-git.txt	9121	0644	edit dl rm
reftable.html	73792	0644	edit dl rm
reftable.txt	37525	0644	edit dl rm
remembering-renames.txt	30360	0644	edit dl rm
repository-version.txt	4311	0644	edit dl rm
rerere.txt	6510	0644	edit dl rm
scalar.html	20458	0644	edit dl rm
scalar.txt	2935	0644	edit dl rm
send-pack-pipeline.html	19315	0644	edit dl rm
send-pack-pipeline.txt	1969	0644	edit dl rm
shallow.html	19685	0644	edit dl rm
shallow.txt	2548	0644	edit dl rm
sparse-checkout.txt	47499	0644	edit dl rm
sparse-index.txt	9501	0644	edit dl rm
trivial-merge.html	22273	0644	edit dl rm
trivial-merge.txt	4264	0644	edit dl rm

Edit: /usr/share/doc/git/technical/send-pack-pipeline.txt (1969B)

Git-send-pack internals
=======================

Overall operation
-----------------

. Connects to the remote side and invokes git-receive-pack.

. Learns what refs the remote has and what commit they point at.
  Matches them to the refspecs we are pushing.

. Checks if there are non-fast-forwards.  Unlike fetch-pack,
  the repository send-pack runs in is supposed to be a superset
  of the recipient in fast-forward cases, so there is no need
  for want/have exchanges, and fast-forward check can be done
  locally.  Tell the result to the other end.

. Calls pack_objects() which generates a packfile and sends it
  over to the other end.

. If the remote side is new enough (v1.1.0 or later), wait for
  the unpack and hook status from the other end.

. Exit with appropriate error codes.

Pack_objects pipeline
---------------------

This function gets one file descriptor (`fd`) which is either a
socket (over the network) or a pipe (local).  What's written to
this fd goes to git-receive-pack to be unpacked.

send-pack ---> fd ---> receive-pack

The function pack_objects creates a pipe and then forks.  The
forked child execs pack-objects with --revs to receive revision
parameters from its standard input. This process will write the
packfile to the other end.

send-pack
       |
       pack_objects() ---> fd ---> receive-pack
          | ^ (pipe)
	  v |
         (child)

The child dup2's to arrange its standard output to go back to
the other end, and read its standard input to come from the
pipe.  After that it exec's pack-objects.  On the other hand,
the parent process, before starting to feed the child pipeline,
closes the reading side of the pipe and fd to receive-pack.

send-pack
       |
       pack_objects(parent)
          |
	  v [0]
         pack-objects [0] ---> receive-pack

[jc: the pipeline was much more complex and needed documentation before
 I understood an earlier bug, but now it is trivial and straightforward.]

cmd: