Re: [PATCH 2/3] commit-graph tests: fix another graph_git_two_modes() helper

Ævar Arnfjörð Bjarmason  [off-list ref] writes:

In 135a7123755 (commit-graph: add --split option to builtin,
2019-06-18) this function was copy/pasted to the split commit-graph
tests, as in the preceding commit we need to fix this to use
&&-chaining, so it won't be hiding errors.

Unlike its sister function in "t5318-commit-graph.sh", which we got
lucky with, this one was hiding a real test failure. A tests added in
c523035cbd8 (commit-graph: allow cross-alternate chains, 2019-06-18)
has never worked as intended. Unlike most other graph_git_behavior
uses in this file it clones the repository into a sub-directory, so
we'll need to refer to "commits/6" as "origin/commits/6".

Interesting.  The original created "fork" prepared the alternates
structure in the preceding test, but tested the "behavour" of the
commands outside the "fork" it just prepared?

 graph_git_two_modes() {
-	git -c core.commitGraph=true $1 >output
-	git -c core.commitGraph=false $1 >expect
+	git ${2:+ -C "$2"} -c core.commitGraph=true $1 >output &&
+	git ${2:+ -C "$2"} -c core.commitGraph=false $1 >expect &&

OK, it was a bit curious to see :+ (instead of just +), but the
caller unconditionally passes "$DIR" (with double quotes), so it is
understandable.  Much more concise than having the caller to repeat
${4+"$4"} where it says "$DIR".