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refs: support symrefs in 'reference-transaction' hook

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The 'reference-transaction' hook runs whenever a reference update is
made to the system. In a previous commit, we added the `old_target` and
`new_target` fields to the `reference_transaction_update()`. In
following commits we'll also add the code to handle symref's in the
reference backends.

Support symrefs also in the 'reference-transaction' hook, by modifying
the current format:
    <old-oid> SP <new-oid> SP <ref-name> LF
to be be:
    <old-value> SP <new-value> SP <ref-name> LF
where for regular refs the output would not change and remain the same.
But when either 'old-value' or 'new-value' is a symref, we print the ref
as 'ref:<ref-target>'.

This does break backward compatibility, but the 'reference-transaction'
hook's documentation always stated that support for symbolic references
may be added in the future.

We do not add any tests in this commit since there is no git command
which activates this flow, in an upcoming commit, we'll start using
transaction based symref updates as the default, we'll add tests there
for the hook too.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Karthik Nayak 2024-05-07 14:58:54 +02:00 committed by Junio C Hamano
parent 57d0b1e2ea
commit a8ae923f85
2 changed files with 25 additions and 9 deletions
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14
Documentation/githooks.txt
View file

@ -486,7 +486,7 @@ 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. The hook
does not cover symbolic references (but that may change in the future).
also supports symbolic reference updates.
The hook takes exactly one argument, which is the current state the
given reference transaction is in:
@ -503,16 +503,20 @@ given reference transaction is in:
For each reference update that was added to the transaction, the hook
receives on standard input a line of the format:
<old-oid> SP <new-oid> SP <ref-name> LF
<old-value> SP <new-value> SP <ref-name> LF
where `<old-oid>` is the old object name passed into the reference
transaction, `<new-oid>` is the new object name to be stored in the
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-oid>` is the all-zeroes object name. To
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`.
For symbolic reference updates the `<old_value>` and `<new-value>`
fields could denote references instead of objects. A reference will be
denoted with a 'ref:' prefix, like `ref:<ref-target>`.
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

20
refs.c
View file

@ -2350,10 +2350,22 @@ static int run_transaction_hook(struct ref_transaction *transaction,
struct ref_update *update = transaction->updates[i];
strbuf_reset(&buf);
strbuf_addf(&buf, "%s %s %s\n",
oid_to_hex(&update->old_oid),
oid_to_hex(&update->new_oid),
update->refname);
if (!(update->flags & REF_HAVE_OLD))
strbuf_addf(&buf, "%s ", oid_to_hex(null_oid()));
else if (update->old_target)
strbuf_addf(&buf, "ref:%s ", update->old_target);
else
strbuf_addf(&buf, "%s ", oid_to_hex(&update->old_oid));
if (!(update->flags & REF_HAVE_NEW))
strbuf_addf(&buf, "%s ", oid_to_hex(null_oid()));
else if (update->new_target)
strbuf_addf(&buf, "ref:%s ", update->new_target);
else
strbuf_addf(&buf, "%s ", oid_to_hex(&update->new_oid));
strbuf_addf(&buf, "%s\n", update->refname);
if (write_in_full(proc.in, buf.buf, buf.len) < 0) {
if (errno != EPIPE) {