[PATCH v4 17/28] trailer: teach iterator about non-trailer lines

From: Linus Arver <linusa@google.com>

Previously the iterator did not iterate over non-trailer lines. This was somewhat unfortunate, because trailer blocks could have non-trailer lines in them since 146245063e (trailer: allow non-trailers in trailer block, 2016-10-21), which was before the iterator was created in f0939a0eb1 (trailer: add interface for iterating over commit trailers, 2020-09-27).

So if trailer API users wanted to iterate over all lines in a trailer block (including non-trailer lines), they could not use the iterator and were forced to use the lower-level trailer_info struct directly (which provides a raw string array that includes all lines in the trailer block).

Change the iterator's behavior so that we also iterate over non-trailer lines, instead of skipping over them. The new "raw" member of the iterator allows API users to access previously inaccessible non-trailer lines. Reword the variable "trailer" to just "line" because this variable can now hold both trailer lines _and_ non-trailer lines.

The new "raw" member is important because anyone currently not using the iterator is using trailer_info's raw string array directly to access lines to check what the combined key + value looks like. If we didn't provide a "raw" member here, iterator users would have to re-construct the unparsed line by concatenating the key and value back together again --- which places an undue burden for iterator users.

The next patch demonstrates the use of the iterator in sequencer.c as an example of where "raw" will be useful, so that it can start using the iterator.

For the existing use of the iterator in builtin/shortlog.c, we don't have to change the code there because that code does

    trailer_iterator_init(&iter, body);
    while (trailer_iterator_advance(&iter)) {
        const char *value = iter.val.buf;

        if (!string_list_has_string(&log->trailers, iter.key.buf))
            continue;

        ...

and the

        if (!string_list_has_string(&log->trailers, iter.key.buf))

condition already skips over non-trailer lines (iter.key.buf is empty for non-trailer lines, making the comparison still work unmodified even with this patch).

Signed-off-by: Linus Arver <linusa@google.com>
---
 trailer.c | 12 +++++-------
 trailer.h |  8 ++++++++
 2 files changed, 13 insertions(+), 7 deletions(-)