Added git.git sha1 lookup method to replace simple binary search in pack backend.

Implemented find_unique_short_oid for pack backend, based on git sha1 lookup method;
finding an object given its full oid is just a particular case of searching
the unique object matching an oid prefix (short oid).

Added git_odb_read_unique_short_oid, which iterates over all the backends to
find and read the unique object matching the given oid prefix.

Added a git_object_lookup_short_oid method to find the unique object in
the repository matching a given oid prefix : it generalizes git_object_lookup
which now does nothing but calls git_object_lookup_short_oid.

2 files changed, 61 insertions, 1 deletions

diff --git a/include/git2/object.h b/include/git2/object.h
index 7fca1c988..4cb6af0ad 100644
--- a/include/git2/object.h
+++ b/include/git2/object.h
@@ -59,6 +59,36 @@ GIT_BEGIN_DECL
 GIT_EXTERN(int) git_object_lookup(git_object **object, git_repository *repo, const git_oid *id, git_otype type);
 
 /**
+ * Lookup a reference to one of the objects in a repostory,
+ * given a prefix of its identifier (short id).
+ *
+ * The object obtained will be so that its identifier
+ * matches the first 'len' hexadecimal characters
+ * (packets of 4 bits) of the given 'id'.
+ * 'len' must be long enough to identify a unique
+ * object matching the prefix; otherwise the method will
+ * fail.
+ *
+ * The generated reference is owned by the repository and
+ * should be closed with the `git_object_close` method
+ * instead of free'd manually.
+ *
+ * The 'type' parameter must match the type of the object
+ * in the odb; the method will fail otherwise.
+ * The special value 'GIT_OBJ_ANY' may be passed to let
+ * the method guess the object's type.
+ *
+ * @param object pointer to the looked-up object
+ * @param repo the repository to look up the object
+ * @param id a short identifier for the object
+ * @param len the length of the short identifier
+ * @param type the type of the object
+ * @return a reference to the object
+ */
+GIT_EXTERN(int) git_object_lookup_short_oid(git_object **object_out, git_repository *repo,
+					const git_oid *id, unsigned int len, git_otype type);
+
+/**
  * Get the id (SHA1) of a repository object
  *
  * @param obj the repository object
diff --git a/include/git2/odb.h b/include/git2/odb.h
index 1d351beea..483934ad3 100644
--- a/include/git2/odb.h
+++ b/include/git2/odb.h
@@ -109,7 +109,7 @@ GIT_EXTERN(void) git_odb_close(git_odb *db);
 /**
  * Read an object from the database.
  *
- * This method queries all avaiable ODB backends
+ * This method queries all available ODB backends
  * trying to read the given OID.
  *
  * The returned object is reference counted and
@@ -126,6 +126,36 @@ GIT_EXTERN(void) git_odb_close(git_odb *db);
 GIT_EXTERN(int) git_odb_read(git_odb_object **out, git_odb *db, const git_oid *id);
 
 /**
+ * Read an object from the database, given a prefix
+ * of its identifier.
+ *
+ * This method queries all available ODB backends
+ * trying to match the 'len' first hexadecimal
+ * characters of the 'short_id'.
+ * The remaining bits (GIT_OID_HEXSZ-len)*4 bits of
+ * 'short_id' must be 0s.
+ * The prefix must be long enough to identify
+ * a unique object in all the backends; the
+ * method will fail otherwise.
+ *
+ * The returned object is reference counted and
+ * internally cached, so it should be closed
+ * by the user once it's no longer in use.
+ *
+ * @param out_oid the oid of the unique object matching
+ * the short id
+ * @param out pointer where to store the read object
+ * @param db database to search for the object in.
+ * @param short_id a prefix of the id of the object to read.
+ * @param len the length of the prefix
+ * @return
+ * - GIT_SUCCESS if the object was read;
+ * - GIT_ENOTFOUND if the object is not in the database.
+ * - GIT_EAMBIGUOUS if the prefix is ambiguous (several objects match the prefix)
+ */
+GIT_EXTERN(int) git_odb_read_unique_short_oid(git_oid *out_oid, git_odb_object **out, git_odb *db, const git_oid *short_id, unsigned int len);
+
+/**
  * Read the header of an object from the database, without
  * reading its full contents.
  *