Fix `scalar diagnose` failures (#543)

This resolves #541.

The root cause here is that this loop that intended to get all files
from the `info` directory of the shared object cache _never worked_, but
previously we did not propagate that to a complete failure.

The reason it didn't work is that we tried to read file contents from
the directory path.

I also noticed a silly retry issue because we are now using `run_git()`
which does three retries due to concurrency issues in the functional
tests. We don't want to repeat failures three times in `scalar
diagnose`.

Makefile

@@ -1351,6 +1351,7 @@ BASIC_CFLAGS += -DSHA1DC_FORCE_ALIGNED_ACCESS
 endif
 ifneq ($(filter leak,$(SANITIZERS)),)
 BASIC_CFLAGS += -DSUPPRESS_ANNOTATED_LEAKS
+BASIC_CFLAGS += -O0
 SANITIZE_LEAK = YesCompiledWithIt
 endif
 ifneq ($(filter address,$(SANITIZERS)),)

diagnose.c

@@ -322,6 +322,8 @@ int create_diagnostics_archive(struct strbuf *zip_path, enum diagnose_mode mode)
 	}
 
 	if (shared_cache) {
+		size_t path_len;
+
 		strbuf_reset(&buf);
 		strbuf_addf(&path, "%s/pack", shared_cache);
 		strbuf_reset(&buf);
@@ -336,6 +338,8 @@ int create_diagnostics_archive(struct strbuf *zip_path, enum diagnose_mode mode)
 
 		strbuf_reset(&path);
 		strbuf_addf(&path, "%s/info", shared_cache);
+		path_len = path.len;
+
 		if (is_directory(path.buf)) {
 			DIR *dir = opendir(path.buf);
 			struct dirent *e;
@@ -343,9 +347,16 @@ int create_diagnostics_archive(struct strbuf *zip_path, enum diagnose_mode mode)
 			while ((e = readdir(dir))) {
 				if (!strcmp(".", e->d_name) || !strcmp("..", e->d_name))
 					continue;
+				if (e->d_type == DT_DIR)
+					continue;
 
 				strbuf_reset(&buf);
 				strbuf_addf(&buf, "--add-virtual-file=info/%s:", e->d_name);
+
+				strbuf_setlen(&path, path_len);
+				strbuf_addch(&path, '/');
+				strbuf_addstr(&path, e->d_name);
+
 				if (strbuf_read_file(&buf, path.buf, 0) < 0) {
 					res = error_errno(_("could not read '%s'"), path.buf);
 					goto diagnose_cleanup;

scalar.c

@@ -930,6 +930,8 @@ static int cmd_diagnose(int argc, const char **argv)
 	setup_enlistment_directory(argc, argv, usage, options, &diagnostics_root);
 	strbuf_addstr(&diagnostics_root, "/.scalarDiagnostics");
 
+	/* Here, a failure should not repeat itself. */
+	git_retries = 1;
 	res = run_git("diagnose", "--mode=all", "-s", "%Y%m%d_%H%M%S",
 		      "-o", diagnostics_root.buf, NULL);