Mark git_oid parameters const when they shouldn't be modified

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

src/git_odb.c

@@ -35,7 +35,7 @@
 
 #include "git_odb.h"
 
-git_result git_odb_sread(git_sobj *out, git_odb *db, git_oid *id)
+git_result git_odb_sread(git_sobj *out, git_odb *db, const git_oid *id)
 {
 	if (!git_odb__sread_packed(out, db, id))
 		return GIT_SUCCESS;

src/git_odb.h

@@ -106,7 +106,7 @@ typedef struct {
  * @return GIT_SUCCESS if the object was read;
  *         GIT_ENOTFOUND if the object is not in the database.
  */
-GIT_EXTERN(git_result) git_odb_sread(git_sobj *out, git_odb *db, git_oid *id);
+GIT_EXTERN(git_result) git_odb_sread(git_sobj *out, git_odb *db, const git_oid *id);
 
 /**
  * Read a small object from the database using only pack files.
@@ -116,7 +116,7 @@ GIT_EXTERN(git_result) git_odb_sread(git_sobj *out, git_odb *db, git_oid *id);
  * @return GIT_SUCCESS if the object was read;
  *         GIT_ENOTFOUND if the object is not in the database.
  */
-GIT_EXTERN(git_result) git_odb__sread_packed(git_sobj *out, git_odb *db, git_oid *id);
+GIT_EXTERN(git_result) git_odb__sread_packed(git_sobj *out, git_odb *db, const git_oid *id);
 
 /**
  * Read a small object from the database using only loose object files.
@@ -126,7 +126,7 @@ GIT_EXTERN(git_result) git_odb__sread_packed(git_sobj *out, git_odb *db, git_oid
  * @return GIT_SUCCESS if the object was read;
  *         GIT_ENOTFOUND if the object is not in the database.
  */
-GIT_EXTERN(git_result) git_odb__sread_loose(git_sobj *out, git_odb *db, git_oid *id);
+GIT_EXTERN(git_result) git_odb__sread_loose(git_sobj *out, git_odb *db, const git_oid *id);
 
 /** @} */
 GIT_END_DECL