survey: expanded TODO list at the bottom of the source file

Signed-off-by: Jeff Hostetler <jeffhostetler@github.com>

builtin/survey.c

@@ -2296,47 +2296,131 @@ int cmd_survey(int argc, const char **argv, const char *prefix)
 }
 
 /*
- * NEEDSWORK: The following is a bit of a laundry list of things
- * that I'd like to add.
+ * NEEDSWORK: So far, I only have iteration on the requested set of
+ * refs and treewalk/reachable objects on that set of refs.  The
+ * following is a bit of a laundry list of things that I'd like to
+ * add.
  *
  * [] Dump stats on all of the packfiles. The number and size of each.
- * Whether each is in the .git directory or in an alternate.  The state
- * of the IDX or MIDX files and etc.  Delta chain stats.  All of this
- * data is relative to the "lived-in" state of the repository.  Stuff
- * that may change after a GC or repack.
+ *    Whether each is in the .git directory or in an alternate.  The
+ *    state of the IDX or MIDX files and etc.  Delta chain stats.  All
+ *    of this data is relative to the "lived-in" state of the
+ *    repository.  Stuff that may change after a GC or repack.
+ *
+ * [] Clone and Index stats. partial, shallow, sparse-checkout,
+ *    sparse-index, etc.  Hydration stats.
  *
  * [] Dump stats on each remote.  When we fetch from a remote the size
- * of the response is related to the set of haves on the server.  You
- * can see this in `GIT_TRACE_CURL=1 git fetch`. We get a `ls-refs`
- * payload that lists all of the branches and tags on the server, so
- * at a minimum the RefName and SHA for each. But for annotated tags
- * we also get the peeled SHA.  The size of this overhead on every
- * fetch is proporational to the size of the `git ls-remote` response
- * (roughly, although the latter repeats the RefName of the peeled
- * tag).  If, for example, you have 500K refs on a remote, you're
- * going to have a long "haves" message, so every fetch will be slow
- * just because of that overhead (not counting new objects to be
- * downloaded).
+ *    of the response is related to the set of haves on the server.
+ *    You can see this in `GIT_TRACE_CURL=1 git fetch`. We get a
+ *    `ls-refs` payload that lists all of the branches and tags on the
+ *    server, so at a minimum the RefName and SHA for each. But for
+ *    annotated tags we also get the peeled SHA.  The size of this
+ *    overhead on every fetch is proporational to the size of the `git
+ *    ls-remote` response (roughly, although the latter repeats the
+ *    RefName of the peeled tag).  If, for example, you have 500K refs
+ *    on a remote, you're going to have a long "haves" message, so
+ *    every fetch will be slow just because of that overhead (not
+ *    counting new objects to be downloaded).
  *
- * Note that the local set of tags in "refs/tags/" is a union over all
- * remotes.  However, since most people only have one remote, we can
- * probaly estimate the overhead value directly from the size of the
- * set of "refs/tags/" that we visited while building the `ref_info`
- * and `ref_array` and not need to ask the remote.
+ *    Note that the local set of tags in "refs/tags/" is a union over
+ *    all remotes.  However, since most people only have one remote,
+ *    we can probaly estimate the overhead value directly from the
+ *    size of the set of "refs/tags/" that we visited while building
+ *    the `ref_info` and `ref_array` and not need to ask the remote.
  *
  * [] Dump info on the complexity of the DAG.  Criss-cross merges.
- * The number of edges that must be touched to compute merge bases.
- * Edge length. The number of parallel lanes in the history that must
- * be navigated to get to the merge base.  What affects the cost of
- * the Ahead/Behind computation?  How often do criss-crosses occur and
- * do they cause various operations to slow down?
+ *    The number of edges that must be touched to compute merge bases.
+ *    Edge length. The number of parallel lanes in the history that
+ *    must be navigated to get to the merge base.  What affects the
+ *    cost of the Ahead/Behind computation?  How often do
+ *    criss-crosses occur and do they cause various operations to slow
+ *    down?
  *
  * [] If there are primary branches (like "main" or "master") are they
- * always on the left side of merges?  Does the graph have a clean
- * left edge?  Or are there normal and "backwards" merges?  Do these
- * cause problems at scale?
+ *    always on the left side of merges?  Does the graph have a clean
+ *    left edge?  Or are there normal and "backwards" merges?  Do
+ *    these cause problems at scale?
  *
  * [] If we have a hierarchy of FI/RI branches like "L1", "L2, ...,
- * can we learn anything about the shape of the repo around these FI
- * and RI integrations?
+ *    can we learn anything about the shape of the repo around these
+ *    FI and RI integrations?
+ *
+ * [] Do we need a no-PII flag to omit pathnames or branch/tag names
+ *    in the various histograms?  (This would turn off --name-rev
+ *    too.)
+ *
+ * [] I have so far avoided adding opinions about individual fields
+ *    (such as the way `git-sizer` prints a row of stars or bangs in
+ *    the last column).
+ *
+ *    I'm wondering if that is a job of this executable or if it
+ *    should be done in a post-processing step using the JSON output.
+ *
+ *    My problem with the `git-sizer` approach is that it doesn't give
+ *    the (casual) user any information on why it has stars or bangs.
+ *    And there isn't a good way to print detailed information in the
+ *    ASCII-art tables that would be easy to understand.
+ *
+ *    [] For example, a large number of refs does not define a cliff.
+ *       Performance will drop off (linearly, quadratically, ... ??).
+ *       The tool should refer them to article(s) talking about the
+ *       different problems that it could cause.  So should `git
+ *       survey` just print the number and (implicitly) refer them to
+ *       the man page (chapter/verse) or to a tool that will interpret
+ *       the number and explain it?
+ *
+ *    [] Alternatively, should `git survey` do that analysis too and
+ *       just print footnotes for each large number?
+ *
+ *    [] The computation of the raw survey JSON data can take HOURS on
+ *       a very large repo (like Windows), so I'm wondering if we
+ *       want to keep the opinion portion separate.
+ *
+ * [] In addition to opinions based on the static data, I would like
+ *    to dump the JSON results (or the Trace2 telemetry) into a DB and
+ *    aggregate it with other users.
+ *
+ *    Granted, they should all see the same DAG and the same set of
+ *    reachable objects, but we could average across all datasets
+ *    generated on a particular date and detect outlier users.
+ *
+ *    [] Maybe someone cloned from the `_full` endpoint rather than
+ *       the limited refs endpoint.
+ *
+ *    [] Maybe that user is having problems with repacking / GC /
+ *       maintenance without knowing it.
+ *
+ * [] I'd also like to dump use the DB to compare survey datasets over
+ *    a time.  How fast is their repository growing and in what ways?
+ *
+ *    [] I'd rather have the delta analysis NOT be inside `git
+ *       survey`, so it makes sense to consider having all of it in a
+ *       post-process step.
+ *
+ * [] Another reason to put the opinion analysis in a post-process
+ *    is that it would be easier to generate plots on the data tables.
+ *    Granted, we can get plots from telemetry, but a stand-alone user
+ *    could run the JSON thru python or jq or something and generate
+ *    something nicer than ASCII-art and it could handle cross-referencing
+ *    and hyperlinking to helpful information on each issue.
+ *
+ * [] I think there are several classes of data that we can report on:
+ *
+ *    [] The "inherit repo properties", such as the shape and size of
+ *       the DAG -- these should be universal in each enlistment.
+ *
+ *    [] The "ODB lived in properties", such as the efficiency
+ *       of the repack and things like partial and shallow clone.
+ *       These will vary, but indicate health of the ODB.
+ *
+ *    [] The "index related properties", such as sparse-checkout,
+ *       sparse-index, cache-tree, untracked-cache, fsmonitor, and
+ *       etc.  These will also vary, but are more like knobs for
+ *       the user to adjust.
+ *
+ *    [] I want to compare these with Matt's "dimensions of scale"
+ *       notes and see if there are other pieces of data that we
+ *       could compute/consider.
+ *
  */