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authorJosh Steadmon <steadmon@google.com>2019-10-03 16:32:57 -0700
committerJunio C Hamano <gitster@pobox.com>2019-10-04 09:26:42 +0900
commit22541013d00bc457fe1fbdc8ac8b79edc069fd7e (patch)
treedd462d67d786ea701dc0a32e4657a907636ab851
parent3d4548e7e29177b6a5e21c73009bc40c63c8ce62 (diff)
downloadgit-22541013d00bc457fe1fbdc8ac8b79edc069fd7e.tar.xz
docs: clarify trace2 version invariants
Make it explicit that we always want trace2 "version" events to be the first event of any trace session. Also list the changes that would or would not cause the EVENT format version field to be incremented. Signed-off-by: Josh Steadmon <steadmon@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--Documentation/technical/api-trace2.txt8
1 files changed, 7 insertions, 1 deletions
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt
index 80ffceada0..18b79128fd 100644
--- a/Documentation/technical/api-trace2.txt
+++ b/Documentation/technical/api-trace2.txt
@@ -604,7 +604,13 @@ only present on the "start" and "atexit" events.
==== Event-Specific Key/Value Pairs
`"version"`::
- This event gives the version of the executable and the EVENT format.
+ This event gives the version of the executable and the EVENT format. It
+ should always be the first event in a trace session. The EVENT format
+ version will be incremented if new event types are added, if existing
+ fields are removed, or if there are significant changes in
+ interpretation of existing events or fields. Smaller changes, such as
+ adding a new field to an existing event, will not require an increment
+ to the EVENT format version.
+
------------
{