tar-tree: Use the prefix field of a tar header

... to store parts of the path, if possible.  This allows us to avoid
writing extended headers in certain cases (long pathes can only be
split at '/' chars).

Also adds a file to the test repo with a 100 chars long directory name.
Even old versions of tar that don't understand POSIX extended headers
should be able to handle this testcase.

Btw.: The longest path in the kernel tree currently has 70 chars.
Together with a 30 chars long prefix this would already cross the
field limit of 100 chars.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/t/t5000-tar-tree.sh b/t/t5000-tar-tree.sh
index adc5e93..278eb66 100755 (executable)
--- a/t/t5000-tar-tree.sh
+++ b/t/t5000-tar-tree.sh
@@ -34,6 +34,9 @@ test_expect_success \
      mkdir a/bin &&
      cp /bin/sh a/bin &&
      ln -s a a/l1 &&
+     (p=long_path_to_a_file && cd a &&
+      for depth in 1 2 3 4 5; do mkdir $p && cd $p; done &&
+      echo text >file_with_long_path) &&
      (cd a && find .) | sort >a.lst'
 
 test_expect_success \

diff --git a/tar-tree.c b/tar-tree.c
index 11bbc81..efab2b5 100644 (file)
--- a/tar-tree.c
+++ b/tar-tree.c
@@ -161,6 +161,16 @@ static unsigned int ustar_header_chksum(const struct ustar_header *header)
        return chksum;
 }
 
+static int get_path_prefix(const struct strbuf *path, int maxlen)
+{
+       int i = path->len;
+       if (i > maxlen)
+               i = maxlen;
+       while (i > 0 && path->buf[i] != '/')
+               i--;
+       return i;
+}
+
 static void write_entry(const unsigned char *sha1, struct strbuf *path,
                         unsigned int mode, void *buffer, unsigned long size)
 {
@@ -195,9 +205,17 @@ static void write_entry(const unsigned char *sha1, struct strbuf *path,
                        return;
                }
                if (path->len > sizeof(header.name)) {
-                       sprintf(header.name, "%s.data", sha1_to_hex(sha1));
-                       strbuf_append_ext_header(&ext_header, "path",
-                                                path->buf, path->len);
+                       int plen = get_path_prefix(path, sizeof(header.prefix));
+                       int rest = path->len - plen - 1;
+                       if (plen > 0 && rest <= sizeof(header.name)) {
+                               memcpy(header.prefix, path->buf, plen);
+                               memcpy(header.name, path->buf + plen + 1, rest);
+                       } else {
+                               sprintf(header.name, "%s.data",
+                                       sha1_to_hex(sha1));
+                               strbuf_append_ext_header(&ext_header, "path",
+                                                        path->buf, path->len);
+                       }
                } else
                        memcpy(header.name, path->buf, path->len);
        }