tree-diff: simplify emit_path() list management

In emit_path() we may append a new combine_diff_path entry to our list, decide that we don't want it (because opt->pathchange() told us so) and then roll it back. Between the addition and the rollback, it doesn't matter if it's in the list or not (no functions can even tell, since it's a singly-linked list and we pass around just the tail entry). So it's much simpler to just wait until opt->pathchange() tells us whether to keep it, and either attach it (or free it) then. We do still have to allocate it up front since it's that struct itself which is passed to the pathchange callback. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Jan 9, 2025 at 03:54 UTC 6632bcba514f4a195447eb77264f75fed3a768e6
1 file changed +5 -6
tree-diff.c
+5 -6
@@ -177,14 +177,12 @@ static struct combine_diff_path *emit_path(struct combine_diff_path *tail,
177
178 if (emitthis) {
179 int keep;
180 - struct combine_diff_path *pprev = tail, *p;
180 + struct combine_diff_path *p;
181
182 strbuf_add(base, path, pathlen);
183 p = combine_diff_path_new(base->buf, base->len, mode,
184 oid ? oid : null_oid(),
185 nparent);
186 - tail->next = p;
187 - tail = p;
186 strbuf_setlen(base, old_baselen);
187
188 for (i = 0; i < nparent; ++i) {
@@ -220,10 +218,11 @@ static struct combine_diff_path *emit_path(struct combine_diff_path *tail,
218 if (opt->pathchange)
219 keep = opt->pathchange(opt, p);
220
223 - if (!keep) {
221 + if (keep) {
222 + tail->next = p;
223 + tail = p;
224 + } else {
225 free(p);
225 - pprev->next = NULL;
226 - tail = pprev;
226 }
227 }
228