[PATCH v2] doc: clarify post-receive hook behavior

The `githooks` documentation mentions that the post-receive hook executes once after git-receive-pack(1) updates all references and that it also receives the same information as the pre-receive hook on standard input. This is misleading though because the hook only executes once if at least one of the attempted reference updates is successful. Also, while each line provided on standard input is in the same format as the pre-receive hook, the information received only includes the set of references that were successfully updated.

Update the documentation to clarify these points and also provide a reference to the post-receive hook section of the `git-receive-pack` documentation which has additional information.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
---

Greetings again,

This is the second version of my patch for post-receive hook documentation updates. Thanks again for taking a look.

-Justin

Changes from v1:
- Removed repetivitve statement about the hook being executed once.
- Slightly reworded statements to improve clarity.

Range-diff against v1:
1:  e4824ba60d ! 1:  747e925dfc doc: clarify post-receive hook behavior
    @@ Documentation/githooks.txt: post-receive
      `git push` and updates reference(s) in its repository.
     -It executes on the remote repository once after all the refs have
     -been updated.
    -+It executes on the remote repository once if any of the attempted ref
    -+updates are successful.
    ++The hook executes on the remote repository once after all the proposed
    ++ref updates are processed and if at least one ref is updated as the
    ++result.
      
     -This hook executes once for the receive operation.  It takes no
     -arguments, but gets the same information as the
     -<<pre-receive,'pre-receive'>>
     -hook does on its standard input.
    -+For a receive operation, this hook executes a single time at most.  It
    -+takes no arguments, but for each ref successfully updated, it receives a
    -+line on standard input that follows the same format as the
    ++The hook takes no arguments.  It receives one line on standard input for
    ++each ref that is successfully updated following the same format as the
     +<<pre-receive,'pre-receive'>> hook.
      
      This hook does not affect the outcome of `git receive-pack`, as it

 Documentation/githooks.txt | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)