[PATCH v2 02/11] commit-graph: change test to die on parse, not load

["Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>]

From: Derrick Stolee <dstolee@microsoft.com>

43d3561 (commit-graph write: don't die if the existing graph is corrupt,
2019-03-25) introduced the GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD environment
variable. This was created to verify that commit-graph was not loaded
when writing a new non-incremental commit-graph.

An upcoming change wants to load a commit-graph in some valuable cases,
but we want to maintain that we don't trust the commit-graph data when
writing our new file. Instead of dying on load, instead die if we ever
try to parse a commit from the commit-graph. This functionally verifies
the same intended behavior, but allows a more advanced feature in the
next change.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 commit-graph.c          | 12 ++++++++----
 commit-graph.h          |  2 +-
 t/t5318-commit-graph.sh |  2 +-
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index d0fedcd9b1..6a28d4a5a6 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -564,10 +564,6 @@ static int prepare_commit_graph(struct repository *r)
 		return !!r->objects->commit_graph;
 	r->objects->commit_graph_attempted = 1;
 
-	if (git_env_bool(GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD, 0))
-		die("dying as requested by the '%s' variable on commit-graph load!",
-		    GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD);
-
 	prepare_repo_settings(r);
 
 	if (!git_env_bool(GIT_TEST_COMMIT_GRAPH, 0) &&
@@ -790,6 +786,14 @@ static int parse_commit_in_graph_one(struct repository *r,
 
 int parse_commit_in_graph(struct repository *r, struct commit *item)
 {
+	static int checked_env = 0;
+
+	if (!checked_env &&
+	    git_env_bool(GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE, 0))
+		die("dying as requested by the '%s' variable on commit-graph parse!",
+		    GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE);
+	checked_env = 1;
+
 	if (!prepare_commit_graph(r))
 		return 0;
 	return parse_commit_in_graph_one(r, r->objects->commit_graph, item);
diff --git a/commit-graph.h b/commit-graph.h
index 881c9b46e5..f0fb13e3f2 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -5,7 +5,7 @@
 #include "object-store.h"
 
 #define GIT_TEST_COMMIT_GRAPH "GIT_TEST_COMMIT_GRAPH"
-#define GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD "GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD"
+#define GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE "GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE"
 #define GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS "GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS"
 
 /*
diff --git a/t/t5318-commit-graph.sh b/t/t5318-commit-graph.sh
index 1073f9e3cf..5ec01abdaa 100755
--- a/t/t5318-commit-graph.sh
+++ b/t/t5318-commit-graph.sh
@@ -436,7 +436,7 @@ corrupt_graph_verify() {
 		cp $objdir/info/commit-graph commit-graph-pre-write-test
 	fi &&
 	git status --short &&
-	GIT_TEST_COMMIT_GRAPH_DIE_ON_LOAD=true git commit-graph write &&
+	GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE=true git commit-graph write &&
 	git commit-graph verify
 }
 
-- 
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