On 6/29/2018 5:54 PM, Stefan Beller wrote:
On Fri, Jun 29, 2018 at 9:13 AM Derrick Stolee <dstolee@xxxxxxxxxxxxx> wrote:
+# Construct a grid-like commit graph with points (x,y)
+# with 1 <= x <= 10, 1 <= y <= 10, where (x,y) has
+# parents (x-1, y) and (x, y-1), keeping in mind that
+# we drop a parent if a coordinate is nonpositive.
+#
+# (10,10)
+# / \
+# (10,9) (9,10)
+# / \ / \
+# (10,8) (9,9) (8,10)
+# / \ / \ / \
+# ( continued...)
+# \ / \ / \ /
+# (3,1) (2,2) (1,3)
+# \ / \ /
+# (2,1) (2,1)
+# \ /
+# (1,1)
+#
+# We use branch 'comit-x-y' to refer to (x,y).
+# This grid allows interesting reachability and
+# non-reachability queries: (x,y) can reach (x',y')
+# if and only if x' <= x and y' <= y.
This is an interesting DAG, though not very common
in reality (81 merges, 18 single parent commits,
one root with a depth of at most 10).
It reminds me of FELINE as that also has 2 independent numbers :)
The design of this graph is exactly so you (the test writer) can know if
two commits can reach exactly by whether the two-dimensional keys are
comparable. It's wide enough that we can come up with interesting test
cases for some of these walks, especially the have/wants negotiation.
I guess it is easy to make up artificial test cases for that,
but I wonder if we want more variety for a generic reachability
test tool (e.g. long chains of parallel histories, octopus,
disconnected parts of the graph)
+test_expect_success 'setup' '
[...]
+ git commit-graph write --reachable
Is this only to test the full commit-graph?, maybe we'd
want to write out the commit graph at (5,10) or so, such
that half the walking is tested without graph.
What about author/commit dates?
There are a lot of ways we can get strange edge cases for commit-graph
walks, especially when we start being clever. This test case is only a
start to feeling like we have good coverage, but having a non-trivial
walk include both outputs (yes/no) for each method is a good start.
I think after we get a basic coverage for these methods on this example,
we can add examples as necessary when we find tricky code paths that
need coverage.
Thanks,
-Stolee
