grep: extract grep_binexp() from grep_or_expr()

When constructing an OR node, the grep.c code uses `grep_or_expr()` to
make a node, assign its kind, and set its left and right children. The
same is not done for AND nodes.

Prepare to introduce a new `grep_and_expr()` function which will share
code with the existing implementation of `grep_or_expr()` by introducing
a new function which compiles either kind of binary expression, and
reimplement `grep_or_expr()` in terms of it.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

grep.c

@@ -603,15 +603,22 @@ static struct grep_expr *grep_not_expr(struct grep_expr *expr)
 	return z;
 }
 
-static struct grep_expr *grep_or_expr(struct grep_expr *left, struct grep_expr *right)
+static struct grep_expr *grep_binexp(enum grep_expr_node kind,
+				     struct grep_expr *left,
+				     struct grep_expr *right)
 {
 	struct grep_expr *z = xcalloc(1, sizeof(*z));
-	z->node = GREP_NODE_OR;
+	z->node = kind;
 	z->u.binary.left = left;
 	z->u.binary.right = right;
 	return z;
 }
 
+static struct grep_expr *grep_or_expr(struct grep_expr *left, struct grep_expr *right)
+{
+	return grep_binexp(GREP_NODE_OR, left, right);
+}
+
 static struct grep_expr *compile_pattern_or(struct grep_pat **);
 static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
 {