checkout: phantom `GIT_ECONFLICT` when `core.symlinks=false` and the index contains symlink entries — status reports the workdir clean, SAFE checkout refuses with "N conflicts prevent checkout"

/* gcc -o repro repro.c -I<include> <libgit2.a> -lpthread -lrt
 * prints:  workdir status entries: 0 (clean)
 *          SAFE checkout B: rc=-13 message="1 conflict prevents checkout"
 */
#include <git2.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

static void die(const char* what, int rc) {
    const git_error* e = git_error_last();
    fprintf(stderr, "%s failed rc=%d: %s\n", what, rc,
            e && e->message ? e->message : "?");
    exit(1);
}

int main(int argc, char** argv) {
    if (argc < 2) { fprintf(stderr, "usage: %s <dir>\n", argv[0]); return 2; }
    git_libgit2_init();
    const char* dir = argv[1];

    git_repository* repo = NULL;
    if (git_repository_init(&repo, dir, 0) != 0) die("init", -1);
    git_config* cfg = NULL;
    if (git_repository_config(&cfg, repo) != 0) die("config", -1);
    git_config_set_bool(cfg, "core.symlinks", 0);   /* sandbox w/o symlink support */
    git_config_set_bool(cfg, "core.filemode", 1);   /* linux-style default */
    git_config_free(cfg);

    git_signature* sig = NULL;
    if (git_signature_new(&sig, "t", "t@t", 1234567890, 0) != 0) die("sig", -1);

    /* commit A: CLAUDE.md (regular) + AGENTS.md (symlink -> CLAUDE.md) */
    git_index* index = NULL;
    if (git_repository_index(&index, repo) != 0) die("index", -1);
    git_oid blobClaude, blobLink, treeA, treeB, commitA, commitB;
    if (git_blob_create_from_buffer(&blobClaude, repo, "hello\n", 6) != 0) die("blob1", -1);
    if (git_blob_create_from_buffer(&blobLink, repo, "CLAUDE.md", 9) != 0) die("blob2", -1);
    git_index_entry e = {0};
    e.mode = GIT_FILEMODE_BLOB; e.id = blobClaude; e.path = "CLAUDE.md";
    if (git_index_add(index, &e) != 0) die("add1", -1);
    memset(&e, 0, sizeof(e));
    e.mode = GIT_FILEMODE_LINK; e.id = blobLink; e.path = "AGENTS.md";
    if (git_index_add(index, &e) != 0) die("add2", -1);
    if (git_index_write_tree(&treeA, index) != 0) die("treeA", -1);
    git_tree* t = NULL;
    if (git_tree_lookup(&t, repo, &treeA) != 0) die("treeA-lookup", -1);
    if (git_commit_create(&commitA, repo, "refs/heads/a", sig, sig, NULL,
                          "A: add AGENTS.md symlink", t, 0, NULL) != 0) die("commitA", -1);
    git_tree_free(t);

    /* commit B: AGENTS.md removed */
    if (git_index_remove(index, "AGENTS.md", 0) != 0) die("rm", -1);
    if (git_index_write_tree(&treeB, index) != 0) die("treeB", -1);
    git_commit* p = NULL;
    if (git_commit_lookup(&p, repo, &commitA) != 0) die("p", -1);
    if (git_tree_lookup(&t, repo, &treeB) != 0) die("treeB-lookup", -1);
    git_commit* parr[1] = { p };
    if (git_commit_create(&commitB, repo, "refs/heads/b", sig, sig, NULL,
                          "B: drop AGENTS.md", t, 1, parr) != 0) die("commitB", -1);
    git_tree_free(t);
    git_commit_free(p);

    /* materialize workdir for commit A like clone/checkout does with
     * core.symlinks=false (fake_symlink -> regular file w/ target text) */
    if (git_repository_set_head(repo, "refs/heads/a") != 0) die("set_head", -1);
    git_object* objA = NULL;
    if (git_object_lookup(&objA, repo, &commitA, GIT_OBJECT_COMMIT) != 0) die("objA", -1);
    git_checkout_options co = GIT_CHECKOUT_OPTIONS_INIT;
    co.checkout_strategy = GIT_CHECKOUT_FORCE;
    int rc = git_checkout_tree(repo, objA, &co);
    if (rc != 0) die("checkout A (FORCE)", rc);
    git_object_free(objA);
    git_tree* tA = NULL;
    if (git_tree_lookup(&tA, repo, &treeA) != 0) die("treeA2", -1);
    if (git_index_read_tree(index, tA) != 0) die("index-restore", -1);
    git_index_write(index);
    git_tree_free(tA);

    /* status must consider the workdir clean */
    git_status_options so = GIT_STATUS_OPTIONS_INIT;
    so.flags = GIT_STATUS_OPT_INCLUDE_UNTRACKED | GIT_STATUS_OPT_RECURSE_UNTRACKED_DIRS;
    git_status_list* sl = NULL;
    if (git_status_list_new(&sl, repo, &so) != 0) die("status", -1);
    size_t dirty = git_status_list_entrycount(sl);
    git_status_list_free(sl);
    printf("workdir status entries: %zu (%s)\n", dirty,
           dirty == 0 ? "clean" : "DIRTY (unexpected)");

    /* SAFE-checkout commit B: AGENTS.md is unmodified -> should be removed, rc=0 */
    git_object* objB = NULL;
    if (git_object_lookup(&objB, repo, &commitB, GIT_OBJECT_COMMIT) != 0) die("objB", -1);
    git_checkout_options cb = GIT_CHECKOUT_OPTIONS_INIT;
    cb.checkout_strategy = GIT_CHECKOUT_SAFE;
    rc = git_checkout_tree(repo, objB, &cb);
    const git_error* err = git_error_last();
    printf("SAFE checkout B: rc=%d message=\"%s\"\n", rc,
           rc == 0 ? "" : (err && err->message ? err->message : "?"));
    git_object_free(objB);

    git_index_free(index);
    git_signature_free(sig);
    git_repository_free(repo);
    git_libgit2_shutdown();
    return rc == 0 ? 0 : 1;
}

workdir status entries: 0 (clean)
SAFE checkout B: rc=-13 message="1 conflict prevents checkout"

git init && git config core.symlinks false
echo hello > CLAUDE.md && git add CLAUDE.md
T=$(printf CLAUDE.md | git hash-object -w --stdin)
git update-index --add --cacheinfo 120000,$T,AGENTS.md
git commit -m A && git branch a
git rm --cached AGENTS.md && git commit -m B
git checkout a && printf CLAUDE.md > AGENTS.md
git status --porcelain   # -> empty (clean)
git checkout master      # -> rc=0, AGENTS.md removed