3 files changed, 10 insertions, 5 deletions
diff --git a/include/git2/object.h b/include/git2/object.h
index 4cb6af0ad..cadb942e0 100644
--- a/include/git2/object.h
+++ b/include/git2/object.h
@@ -65,9 +65,9 @@ GIT_EXTERN(int) git_object_lookup(git_object **object, git_repository *repo, con
  * 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.
+ * 'len' must be at least GIT_OID_MINPREFIXLEN, and
+ * 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
diff --git a/include/git2/odb.h b/include/git2/odb.h
index 483934ad3..6c08ade54 100644
--- a/include/git2/odb.h
+++ b/include/git2/odb.h
@@ -132,9 +132,10 @@ GIT_EXTERN(int) git_odb_read(git_odb_object **out, git_odb *db, const git_oid *i
  * 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
+ * The remaining (GIT_OID_HEXSZ-len)*4 bits of
  * 'short_id' must be 0s.
- * The prefix must be long enough to identify
+ * 'len' must be at least GIT_OID_MINPREFIXLEN,
+ * and the prefix must be long enough to identify
  * a unique object in all the backends; the
  * method will fail otherwise.
  *
diff --git a/include/git2/oid.h b/include/git2/oid.h
index e8803ced8..062b9ca8b 100644
--- a/include/git2/oid.h
+++ b/include/git2/oid.h
@@ -43,6 +43,10 @@ GIT_BEGIN_DECL
 /** Size (in bytes) of a hex formatted oid */
 #define GIT_OID_HEXSZ (GIT_OID_RAWSZ * 2)
 
+/** Minimum length (in number of hex characters,
+ * i.e. packets of 4 bits) of an oid prefix */
+#define GIT_OID_MINPREFIXLEN 4
+
 /** Unique identity of any object (commit, tree, blob, tag). */
 typedef struct {
 	/** raw binary formatted id */