[v2,06/27] fsmonitor-settings: VFS for Git virtual repos are incompatible

Commit Message

Jeff Hostetler March 8, 2022, 10:15 p.m. UTC

From: Jeff Hostetler <[e-mail]>

VFS for Git virtual repositories are incompatible with FSMonitor.

VFS for Git is a downstream fork of Git.  It contains its own custom
file system watcher that is aware of the virtualization.  If a working
directory is being managed by VFS for Git, we should not try to watch
it because we may get incomplete results.

We do not know anything about how VFS for Git works, but we do
know that VFS for Git working directories contain a well-defined
config setting.  If it is set, mark the working directory as
incompatible.

Signed-off-by: Jeff Hostetler <[e-mail]>
---
 compat/fsmonitor/fsm-settings-win32.c | 26 ++++++++++++++++++++++++++
 fsmonitor-settings.c                  |  3 +++
 fsmonitor-settings.h                  |  1 +
 t/t7519-status-fsmonitor.sh           |  9 +++++++++
 4 files changed, 39 insertions(+)

Patch

diff --git a/compat/fsmonitor/fsm-settings-win32.c b/compat/fsmonitor/fsm-settings-win32.c
index 7fce32a3c5b..ee78bba38e3 100644
--- a/compat/fsmonitor/fsm-settings-win32.c
+++ b/compat/fsmonitor/fsm-settings-win32.c
@@ -3,7 +3,33 @@ 
 #include "repository.h"
 #include "fsmonitor-settings.h"
 
+/*
+ * VFS for Git is incompatible with FSMonitor.
+ *
+ * Granted, core Git does not know anything about VFS for Git and we
+ * shouldn't make assumptions about a downstream feature, but users
+ * can install both versions.  And this can lead to incorrect results
+ * from core Git commands.  So, without bringing in any of the VFS for
+ * Git code, do a simple config test for a published config setting.
+ * (We do not look at the various *_TEST_* environment variables.)
+ */
+static enum fsmonitor_reason check_vfs4git(struct repository *r)
+{
+	const char *const_str;
+
+	if (!repo_config_get_value(r, "core.virtualfilesystem", &const_str))
+		return FSMONITOR_REASON_VFS4GIT;
+
+	return FSMONITOR_REASON_OK;
+}
+
 enum fsmonitor_reason fsm_os__incompatible(struct repository *r)
 {
+	enum fsmonitor_reason reason;
+
+	reason = check_vfs4git(r);
+	if (reason != FSMONITOR_REASON_OK)
+		return reason;
+
 	return FSMONITOR_REASON_OK;
 }
diff --git a/fsmonitor-settings.c b/fsmonitor-settings.c
index 1b16b551d87..ea3e365dfc4 100644
--- a/fsmonitor-settings.c
+++ b/fsmonitor-settings.c
@@ -177,6 +177,9 @@  const char *fsm_settings__get_reason_msg(struct repository *r)
 
 	case FSMONITOR_REASON_BARE:
 		return _("bare repos are incompatible with fsmonitor");
+
+	case FSMONITOR_REASON_VFS4GIT:
+		return _("virtual repos are incompatible with fsmonitor");
 	}
 
 	BUG("Unhandled case in fsm_settings__get_reason_msg '%d'",
diff --git a/fsmonitor-settings.h b/fsmonitor-settings.h
index be25272c012..7950529611b 100644
--- a/fsmonitor-settings.h
+++ b/fsmonitor-settings.h
@@ -16,6 +16,7 @@  enum fsmonitor_mode {
 enum fsmonitor_reason {
 	FSMONITOR_REASON_OK = 0, /* no incompatibility or when disbled */
 	FSMONITOR_REASON_BARE,
+	FSMONITOR_REASON_VFS4GIT, /* VFS for Git virtualization */
 };
 
 void fsm_settings__set_ipc(struct repository *r);
diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
index cf258d88f04..285508fb67e 100755
--- a/t/t7519-status-fsmonitor.sh
+++ b/t/t7519-status-fsmonitor.sh
@@ -78,6 +78,15 @@  test_expect_success FSMONITOR_DAEMON 'run fsmonitor-daemon in bare repo' '
 	grep "bare repos are incompatible with fsmonitor" actual
 '
 
+test_expect_success MINGW,FSMONITOR_DAEMON 'run fsmonitor-daemon in virtual repo' '
+	test_when_finished "rm -rf ./fake-virtual-clone actual" &&
+	git init fake-virtual-clone &&
+	test_must_fail git -C ./fake-virtual-clone \
+			   -c core.virtualfilesystem=true \
+			   fsmonitor--daemon run 2>actual &&
+	grep "virtual repos are incompatible with fsmonitor" actual
+'
+
 test_expect_success 'setup' '
 	mkdir -p .git/hooks &&
 	: >tracked &&