challenge: Add "--diff".

* guix/scripts/challenge.scm (dump-port*): New variable.
(archive-contents, store-item-contents, narinfo-contents)
(differing-files, report-differing-files): New procedures.
(summarize-report): Add #:report-differences and call it.
(show-help, %options): Add "--diff".
(%default-options): Add 'difference-report' key.
(report-differing-files): Parameterize CURRENT-TERMINAL-COLUMNS and pass
 #:report-differences to 'summarize-report'.
* guix/tests/http.scm (%local-url): Add optional argument.
(call-with-http-server): Fix docstring typo.
* tests/challenge.scm (query-path-size, make-narinfo): New procedures.
("differing-files"): New test.
* doc/guix.texi (Invoking guix challenge): Document "--diff".

1 files changed, 24 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index cb51878004..80d67a44fa 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10321,14 +10321,23 @@ updating list of substitutes from 'https://guix.example.org'... 100.0%
   local hash: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
   https://@value{SUBSTITUTE-SERVER}/nar/@dots{}-openssl-1.0.2d: 0725l22r5jnzazaacncwsvp9kgf42266ayyp814v7djxs7nk963q
   https://guix.example.org/nar/@dots{}-openssl-1.0.2d: 1zy4fmaaqcnjrzzajkdn3f5gmjk754b43qkq47llbyak9z0qjyim
+  differing files:
+    /lib/libcrypto.so.1.1
+    /lib/libssl.so.1.1
+
 /gnu/store/@dots{}-git-2.5.0 contents differ:
   local hash: 00p3bmryhjxrhpn2gxs2fy0a15lnip05l97205pgbk5ra395hyha
   https://@value{SUBSTITUTE-SERVER}/nar/@dots{}-git-2.5.0: 069nb85bv4d4a6slrwjdy8v1cn4cwspm3kdbmyb81d6zckj3nq9f
   https://guix.example.org/nar/@dots{}-git-2.5.0: 0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73
+  differing file:
+    /libexec/git-core/git-fsck
+
 /gnu/store/@dots{}-pius-2.1.1 contents differ:
   local hash: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
   https://@value{SUBSTITUTE-SERVER}/nar/@dots{}-pius-2.1.1: 0k4v3m9z1zp8xzzizb7d8kjj72f9172xv078sq4wl73vnq9ig3ax
   https://guix.example.org/nar/@dots{}-pius-2.1.1: 1cy25x1a4fzq5rk0pmvc8xhwyffnqz95h2bpvqsz2mpvlbccy0gs
+  differing file:
+    /share/man/man1/pius.1.gz
 
 @dots{}
 
@@ -10414,6 +10423,21 @@ The one option that matters is:
 Consider @var{urls} the whitespace-separated list of substitute source
 URLs to compare to.
 
+@item --diff=@var{mode}
+Upon mismatches, show differences according to @var{mode}, one of:
+
+@table @asis
+@item @code{simple} (the default)
+Show the list of files that differ.
+
+@item @code{none}
+Do not show further details about the differences.
+@end table
+
+Thus, unless @code{--diff=none} is passed, @command{guix challenge}
+downloads the store items from the given substitute servers so that it
+can compare them.
+
 @item --verbose
 @itemx -v
 Show details about matches (identical contents) in addition to