Grow block count to configured value when LFS_M_GROW mount flag is set

[kaetemi]

See #279

[kaetemi]

Test

    err = lfs_mount(&lfs, &cfg);
    lfs_unmount(&lfs);

    // fail without flag
    cfg.block_count += 1;
    err = lfs_mount(&lfs, &cfg);
    assert(err);

    // success with flag
    cfg.flags |= LFS_M_GROW;
    err = lfs_mount(&lfs, &cfg);
    assert(err == LFS_ERR_OK);
    lfs_unmount(&lfs);

    // cannot shrink
    cfg.flags = 0;
    cfg.block_count -= 1;
    err = lfs_mount(&lfs, &cfg);
    assert(err);

    // cannot shrink with flag either
    cfg.flags |= LFS_M_GROW;
    err = lfs_mount(&lfs, &cfg);
    assert(err);

[geky]

Hi @kaetemi, thanks for the PR. This is a great implementation, but unfortunately I'm against the resizing behavior being implicit. I've added a comment with more info to the related issue #279.

I can modify this to be in a separate lfs_fs_grow function if you don't beat me to it.

I'm also hoping to address #349 in the next minor release, which means lfs_mount will probably have quite a few changes.

[geky]

I've gone ahead and added lfs_fs_grow to #753, thanks for the original PR. I believe #753 replaces this now, but let me know if I'm missing anything.

[geky]

Closing as this has been merged into #872 and should be mainlined shortly as a part of #877.

Feel free to reopen if you think I missed anything and thanks again for the PR!