githooks.txt: clarify documentation on reference-transaction hook

index 4dad80052e..b51959ff94 100644 --- a/Documentation/githooks.txt +++ b/Documentation/githooks.txt @@ -473,7 +473,8 @@ reference-transaction This hook is invoked by any Git command that performs reference updates. It executes whenever a reference transaction is prepared, -committed or aborted and may thus get called multiple times. +committed or aborted and may thus get called multiple times. The hook +does not cover symbolic references (but that may change in the future). The hook takes exactly one argument, which is the current state the given reference transaction is in: @@ -492,6 +493,14 @@ receives on standard input a line of the format: <old-value> SP <new-value> SP <ref-name> LF +where `<old-value>` is the old object name passed into the reference +transaction, `<new-value>` is the new object name to be stored in the +ref and `<ref-name>` is the full name of the ref. When force updating +the reference regardless of its current value or when the reference is +to be created anew, `<old-value>` is the all-zeroes object name. To +distinguish these cases, you can inspect the current value of +`<ref-name>` via `git rev-parse`. + The exit status of the hook is ignored for any state except for the "prepared" state. In the "prepared" state, a non-zero exit status will cause the transaction to be aborted. The hook will not be called with