Change spelling from "commit'ish" to "commit-ish"

Since the hyphen spelling is what the official Git docs use.

This change affects only docstrings.

Author: EliahKagan

Diff for: git/index/base.py

@@ -1300,7 +1300,7 @@ def reset(
             but if True, this method behaves like HEAD.reset.
 
         :param paths: if given as an iterable of absolute or repository-relative paths,
-            only these will be reset to their state at the given commit'ish.
+            only these will be reset to their state at the given commit-ish.
             The paths need to exist at the commit, otherwise an exception will be
             raised.
 

Diff for: git/objects/submodule/base.py

@@ -1095,7 +1095,7 @@ def set_parent_commit(self, commit: Union[Commit_ish, None], check: bool = True)
         contain the .gitmodules blob.
 
         :param commit:
-            Commit'ish reference pointing at the root_tree, or None to always point to the
+            Commit-ish reference pointing at the root_tree, or None to always point to the
             most recent commit
         :param check:
             if True, relatively expensive checks will be performed to verify

Diff for: git/objects/submodule/root.py

@@ -91,7 +91,7 @@ def update(
         Additionally it will detect addition and removal of submodules, which will be handled
         gracefully.
 
-        :param previous_commit: If set to a commit'ish, the commit we should use
+        :param previous_commit: If set to a commit-ish, the commit we should use
             as the previous commit the HEAD pointed to before it was set to the commit it points to now.
             If None, it defaults to HEAD@{1} otherwise
         :param recursive: if True, the children of submodules will be updated as well

Diff for: git/refs/symbolic.py

@@ -641,7 +641,7 @@ def create(
 
         :param reference:
             The reference to which the new symbolic reference should point to.
-            If it is a commit'ish, the symbolic ref will be detached.
+            If it is a commit-ish, the symbolic ref will be detached.
 
         :param force:
             if True, force creation even if a symbolic reference with that name already exists.