[PATCH v4 0/5] Fixes for Documentation/MyFirstObjectWalk.txt

The 4th round of this series.

Chances are that I just waste your time with my attemt [4/5]. My appologies in advance, should this be the case.

Recently, there was a discussion [1] on the groff mailing list and I guess I couldn't resist to try to practice what I read in the linked resources ;-)

[1] https://lists.gnu.org/archive/html/groff/2024-03/msg00014.html

Could be that the remaining controversal part of [4/5] should just be left untouched, because it is consuming so much time -- I summarized all those versions, so that all incarnations can be compared in one view:

* Original:

Asking `traverse_commit_list_filtered()` to populate the `omitted` list means that our object walk does not perform any better than an unfiltered object walk; all reachable objects are walked in order to populate the list.

* v3:

Note that this means that our object walk will not perform any better than an unfiltered object walk; all reachable objects are walked in order to populate the list.

* Junio's suggestion (with minor rearrangement):

Note that our object walk with this function will not perform any better than the previous unfiltered walk, because all reachable objects need to be walked in order to populate the list of filtered objects.

* Kyle's suggestion:

Note that requesting the list of filtered objects may have performance implications; all reachable objects will be visited in order to populate the list of filtered objects.

* My new attempt (v4):

This list of filtered objects may have performance implications, however, because despite filtering objects, the possibly much larger set of all reachable objects must be processed in order to populate that list.

--
Changes in v4:
* Used the proper `git show` for references in [1/5] and [3/5]
* Another attempt to write clear speach in [4/5]

Changes in v3:
* Reword the description in [4/5]
* Add a missing slash in [5/5]

Changes in v2:
* Added Emily to Cc in the hope for a review
* Remove superfluous tags from [1/5] and [3/5]
* Replace bashism `|&` by `2>&1 |` in [5/5]
--
Dirk Gouders (5):
  MyFirstObjectWalk: use additional arg in config_fn_t
  MyFirstObjectWalk: fix misspelled "builtins/"
  MyFirstObjectWalk: fix filtered object walk
  MyFirstObjectWalk: fix description for counting omitted objects
  MyFirstObjectWalk: add stderr to pipe processing

 Documentation/MyFirstObjectWalk.txt | 37 ++++++++++++++++-------------
 1 file changed, 21 insertions(+), 16 deletions(-)

Range-diff against v3:
1:  0eeb4b78ac ! 1:  102cbc54c4 MyFirstObjectWalk: use additional arg in config_fn_t
    @@ Metadata
      ## Commit message ##
         MyFirstObjectWalk: use additional arg in config_fn_t
     
    -    Commit a4e7e317 (config: add ctx arg to config_fn_t) added a fourth
    -    argument to config_fn_t but did not change relevant function calls
    -    in Documentation/MyFirstObjectWalk.txt.
    +    Commit a4e7e317f8 (config: add ctx arg to config_fn_t, 2023-06-28)
    +    added a fourth argument to config_fn_t but did not change relevant
    +    function calls in Documentation/MyFirstObjectWalk.txt.
     
         Fix those calls and the example git_walken_config() to use
         that additional argument.
2:  3122ae2472 = 2:  5fb7953f31 MyFirstObjectWalk: fix misspelled "builtins/"
3:  f21348ab80 ! 3:  b88518df0b MyFirstObjectWalk: fix filtered object walk
    @@ Metadata
      ## Commit message ##
         MyFirstObjectWalk: fix filtered object walk
     
    -    Commit f0d2f849 (MyFirstObjectWalk: update recommended usage)
    -    changed a call of parse_list_objects_filter() in a way that
    -    probably never worked: parse_list_objects_filter() always needed a
    -    pointer as its first argument.
    +    Commit f0d2f84919 (MyFirstObjectWalk: update recommended usage,
    +    2022-03-09) changed a call of parse_list_objects_filter() in a way
    +    that probably never worked: parse_list_objects_filter() always needed
    +    a pointer as its first argument.
     
         Fix this by removing the CALLOC_ARRAY and passing the address of
         rev->filter to parse_list_objects_filter() in accordance to
4:  cfa4b9ce50 ! 4:  11510630af MyFirstObjectWalk: fix description for counting omitted objects
    @@ Documentation/MyFirstObjectWalk.txt: points to the same tree object as its grand
     -reachable objects are walked in order to populate the list.
     +filter, like with `git log --filter=<spec> --filter-print-omitted`. To do this,
     +change `traverse_commit_list()` to `traverse_commit_list_filtered()`, which is
    -+able to populate an `omitted` list. Note that this means that our object walk
    -+will not perform any better than an unfiltered object walk; all reachable
    -+objects are walked in order to populate the list.
    ++able to populate an `omitted` list.  This list of filtered objects may have
    ++performance implications, however, because despite filtering objects, the possibly
    ++much larger set of all reachable objects must be processed in order to
    ++populate that list.
      
      First, add the `struct oidset` and related items we will use to iterate it:
      
5:  c571abb49d = 5:  8920313ee2 MyFirstObjectWalk: add stderr to pipe processing