Remove 'working copy' from the documentation and C code

The git term is 'working tree', so replace the most public references
to 'working copy'.

Signed-off-by: Carlos Martín Nieto <cmn@elego.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -147,7 +147,7 @@ advice.*::
 
 core.fileMode::
 	If false, the executable bit differences between the index and
-	the working copy are ignored; useful on broken filesystems like FAT.
+	the working tree are ignored; useful on broken filesystems like FAT.
 	See linkgit:git-update-index[1].
 +
 The default is true, except linkgit:git-clone[1] or linkgit:git-init[1]
@@ -179,7 +179,7 @@ is created.
 
 core.trustctime::
 	If false, the ctime differences between the index and the
-	working copy are ignored; useful when the inode change time
+	working tree are ignored; useful when the inode change time
 	is regularly modified by something outside Git (file system
 	crawlers and some backup systems).
 	See linkgit:git-update-index[1]. True by default.
@@ -292,7 +292,7 @@ core.ignoreStat::
 	If true, commands which modify both the working tree and the index
 	will mark the updated paths with the "assume unchanged" bit in the
 	index. These marked files are then assumed to stay unchanged in the
-	working copy, until you	mark them otherwise manually - Git will not
+	working tree, until you mark them otherwise manually - Git will not
 	detect the file changes	by lstat() calls. This is useful on systems
 	where those are very slow, such as Microsoft Windows.
 	See linkgit:git-update-index[1].

Documentation/git-svn.txt

@@ -318,7 +318,7 @@ Any other arguments are passed directly to 'git log'
        Show what revision and author last modified each line of a file. The
        output of this mode is format-compatible with the output of
        `svn blame' by default. Like the SVN blame command,
-       local uncommitted changes in the working copy are ignored;
+       local uncommitted changes in the working tree are ignored;
        the version of the file in the HEAD revision is annotated. Unknown
        arguments are passed directly to 'git blame'.
 +

diff-lib.c

@@ -289,7 +289,7 @@ static void show_new_file(struct rev_info *revs,
 
 	/*
 	 * New file in the index: it might actually be different in
-	 * the working copy.
+	 * the working tree.
 	 */
 	if (get_stat_data(new, &sha1, &mode, cached, match_missing,
 	    &dirty_submodule, &revs->diffopt) < 0)

merge-recursive.c

@@ -390,7 +390,7 @@ static void record_df_conflict_files(struct merge_options *o,
 				     struct string_list *entries)
 {
 	/* If there is a D/F conflict and the file for such a conflict
-	 * currently exist in the working copy, we want to allow it to be
+	 * currently exist in the working tree, we want to allow it to be
 	 * removed to make room for the corresponding directory if needed.
 	 * The files underneath the directories of such D/F conflicts will
 	 * be processed before the corresponding file involved in the D/F