Drop unused git-rebase--am.sh

Since 2185362 (built-in rebase: call `git am` directly, 2019-01-18),
the built-in rebase already uses the built-in `git am` directly.

Now that d03ebd4 (rebase: remove the rebase.useBuiltin setting,
2019-03-18) even removed the scripted rebase, there is no longer any
user of `git-rebase--am.sh`, so let's just remove it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.gitignore

@@ -122,7 +122,6 @@
 /git-range-diff
 /git-read-tree
 /git-rebase
-/git-rebase--am
 /git-rebase--common
 /git-rebase--interactive
 /git-rebase--preserve-merges

Makefile

@@ -624,7 +624,6 @@ SCRIPT_SH += git-web--browse.sh
 
 SCRIPT_LIB += git-mergetool--lib
 SCRIPT_LIB += git-parse-remote
-SCRIPT_LIB += git-rebase--am
 SCRIPT_LIB += git-rebase--common
 SCRIPT_LIB += git-rebase--preserve-merges
 SCRIPT_LIB += git-sh-setup

builtin/rebase.c

@@ -1153,10 +1153,6 @@ static int run_specific_rebase(struct rebase_options *opts, enum action action)
 	}
 
 	switch (opts->type) {
-	case REBASE_AM:
-		backend = "git-rebase--am";
-		backend_func = "git_rebase__am";
-		break;
 	case REBASE_PRESERVE_MERGES:
 		backend = "git-rebase--preserve-merges";
 		backend_func = "git_rebase__preserve_merges";