[PATCH v2] refs: make explicit that ref_iterator_peel returns boolean

From: Han-Wen Nienhuys <hanwen@google.com>

Use -1 as error return value throughout.

This removes spurious differences in the GIT_TRACE_REFS output, depending on the ref storage backend active.

Before, the cached ref_iterator (but only that iterator!) would return peel_object() output directly. No callers relied on the peel_status values beyond success/failure. All calls to these functions go through peel_iterated_oid(), which returns peel_object() as a fallback, but also squashing the error values.

The iteration interface already passes REF_ISSYMREF and REF_ISBROKEN through the flags argument, so the additional error values in enum peel_status provide no value.

The ref iteration interface provides a separate peel() function because certain formats (eg. packed-refs and reftable) can store the peeled object next to the tag SHA1. Passing the peeled SHA1 as an optional argument to each_ref_fn maps more naturally to the implementation of ref databases. Changing the code in this way is left for a future refactoring.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
---
    refs: ref_iterator_peel returns boolean, rather than peel_status
    
    v2: expand commit message.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1006%2Fhanwen%2Fpeel_return-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1006/hanwen/peel_return-v2
Pull-Request: https://github.com/git/git/pull/1006

Range-diff vs v1:

 1:  241e0ad1954b ! 1:  f1dc6c2d7fea refs: ref_iterator_peel returns boolean, rather than peel_status
     @@ Metadata
      Author: Han-Wen Nienhuys <hanwen@google.com>
      
       ## Commit message ##
     -    refs: ref_iterator_peel returns boolean, rather than peel_status
     +    refs: make explicit that ref_iterator_peel returns boolean
      
     -    Before, the cached ref_iterator would return peel_object() output directly. This
     -    led to spurious differences in the GIT_TRACE_REFS output, depending on the ref
     -    storage backend active.
     +    Use -1 as error return value throughout.
     +
     +    This removes spurious differences in the GIT_TRACE_REFS output, depending on the
     +    ref storage backend active.
     +
     +    Before, the cached ref_iterator (but only that iterator!) would return
     +    peel_object() output directly. No callers relied on the peel_status values
     +    beyond success/failure. All calls to these functions go through
     +    peel_iterated_oid(), which returns peel_object() as a fallback, but also
     +    squashing the error values.
     +
     +    The iteration interface already passes REF_ISSYMREF and REF_ISBROKEN through the
     +    flags argument, so the additional error values in enum peel_status provide no
     +    value.
     +
     +    The ref iteration interface provides a separate peel() function because certain
     +    formats (eg. packed-refs and reftable) can store the peeled object next to the
     +    tag SHA1. Passing the peeled SHA1 as an optional argument to each_ref_fn maps
     +    more naturally to the implementation of ref databases. Changing the code in this
     +    way is left for a future refactoring.
      
          Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
      
     @@ refs.c: int peel_iterated_oid(const struct object_id *base, struct object_id *pe
       		return ref_iterator_peel(current_ref_iter, peeled);
       
      -	return peel_object(base, peeled);
     -+	return !!peel_object(base, peeled);
     ++	return peel_object(base, peeled) ? -1 : 0;
       }
       
       int refs_create_symref(struct ref_store *refs,
      
     + ## refs/packed-backend.c ##
     +@@ refs/packed-backend.c: static int packed_ref_iterator_peel(struct ref_iterator *ref_iterator,
     + 	} else if ((iter->base.flags & (REF_ISBROKEN | REF_ISSYMREF))) {
     + 		return -1;
     + 	} else {
     +-		return !!peel_object(&iter->oid, peeled);
     ++		return peel_object(&iter->oid, peeled) ? -1 : 0;
     + 	}
     + }
     + 
     +
       ## refs/ref-cache.c ##
      @@ refs/ref-cache.c: static int cache_ref_iterator_advance(struct ref_iterator *ref_iterator)
       static int cache_ref_iterator_peel(struct ref_iterator *ref_iterator,
       				   struct object_id *peeled)
       {
      -	return peel_object(ref_iterator->oid, peeled);
     -+	return !!peel_object(ref_iterator->oid, peeled);
     ++	return peel_object(ref_iterator->oid, peeled) ? -1 : 0;
       }
       
       static int cache_ref_iterator_abort(struct ref_iterator *ref_iterator)
     @@ refs/refs-internal.h: void base_ref_iterator_free(struct ref_iterator *iter);
       typedef int ref_iterator_advance_fn(struct ref_iterator *ref_iterator);
       
      +/*
     -+ * Peels the current ref, returning 0 for success.
     ++ * Peels the current ref, returning 0 for success or -1 for failure.
      + */
       typedef int ref_iterator_peel_fn(struct ref_iterator *ref_iterator,
       				 struct object_id *peeled);

 refs.c                | 2 +-
 refs/packed-backend.c | 2 +-
 refs/ref-cache.c      | 2 +-
 refs/refs-internal.h  | 3 +++
 4 files changed, 6 insertions(+), 3 deletions(-)