builtin-am: implement --[no-]message-id, am.messageid

diff --git a/strbuf.c b/strbuf.c
index 0d4f4e54ec1ff1f0d37155e8049476d802a7c7e5..cce5eed14a4cc53d3b7d04cb8a14ea8aa9f69e52 100644 (file)
--- a/strbuf.c
+++ b/strbuf.c
@@ -526,9 +526,10 @@ int strbuf_getwholeline_fd(struct strbuf *sb, int fd, int term)
        return 0;
 }
 
-int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
+ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
 {
-       int fd, len;
+       int fd;
+       ssize_t len;
 
        fd = open(path, O_RDONLY);
        if (fd < 0)
@@ -709,3 +710,36 @@ char *xstrfmt(const char *fmt, ...)
 
        return ret;
 }
+
+void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
+{
+       size_t hint = 128;
+       size_t len;
+
+       if (!*fmt)
+               return;
+
+       strbuf_grow(sb, hint);
+       len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm);
+
+       if (!len) {
+               /*
+                * strftime reports "0" if it could not fit the result in the buffer.
+                * Unfortunately, it also reports "0" if the requested time string
+                * takes 0 bytes. So our strategy is to munge the format so that the
+                * output contains at least one character, and then drop the extra
+                * character before returning.
+                */
+               struct strbuf munged_fmt = STRBUF_INIT;
+               strbuf_addf(&munged_fmt, "%s ", fmt);
+               while (!len) {
+                       hint *= 2;
+                       strbuf_grow(sb, hint);
+                       len = strftime(sb->buf + sb->len, sb->alloc - sb->len,
+                                      munged_fmt.buf, tm);
+               }
+               strbuf_release(&munged_fmt);
+               len--; /* drop munged space */
+       }
+       strbuf_setlen(sb, sb->len + len);
+}