From f6c013dfa1a002661543ad5504a918636099c91b Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Tue, 12 Oct 2021 19:06:01 -0700 Subject: signature-format.txt: explain and illustrate multi-line headers A signature attached to a signed commit, and the contents of the commit that merged a signed tag, are both recorded as a value of an object header field as a multi-line value, and are subject to the formatting convention for multi-line values in the headers, with a leading SP signaling that the rest of the line is a continuation of the previous line. Most notably, an empty line in such a multi-line value would result in a line with a sole SP on it. Examples in the signature-format technical documentation include a few of these cases but we did not show these otherwise invisible SPs in the example. These trailing spaces cannot be seen on display or on paper, and forces the readers to look for them in their editors or pagers, even if we added them to the document. Extend the overview section to explain the multi-line value formatting and highlight these otherwise invisible SPs by inventing the "a dollar-sign at the end of line that appears after SP merely signals that there is a SP there, and the dollar-sign itself does not appear in the real file" notation, inspired by "cat -e" output, to help readers to learn exactly where such "a single SP that is originally an empty line" appears in the examples. Reported-by: Rob Browning Signed-off-by: Junio C Hamano --- Documentation/technical/signature-format.txt | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) (limited to 'Documentation/technical') diff --git a/Documentation/technical/signature-format.txt b/Documentation/technical/signature-format.txt index 2c9406a56a..166721be6f 100644 --- a/Documentation/technical/signature-format.txt +++ b/Documentation/technical/signature-format.txt @@ -13,6 +13,22 @@ Signatures always begin with `-----BEGIN PGP SIGNATURE-----` and end with `-----END PGP SIGNATURE-----`, unless gpg is told to produce RFC1991 signatures which use `MESSAGE` instead of `SIGNATURE`. +Signatures sometimes appear as a part of the normal payload +(e.g. a signed tag has the signature block appended after the payload +that the signature applies to), and sometimes appear in the value of +an object header (e.g. a merge commit that merged a signed tag would +have the entire tag contents on its "mergetag" header). In the case +of the latter, the usual multi-line formatting rule for object +headers applies. I.e. the second and subsequent lines are prefixed +with a SP to signal that the line is continued from the previous +line. + +This is even true for an originally empty line. In the following +examples, the end of line that ends with a whitespace letter is +highlighted with a `$` sign; if you are trying to recreate these +example by hand, do not cut and paste them---they are there +primarily to highlight extra whitespace at the end of some lines. + The signed payload and the way the signature is embedded depends on the type of the object resp. transaction. @@ -78,7 +94,7 @@ author A U Thor 1465981137 +0000 committer C O Mitter 1465981137 +0000 gpgsig -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 - + $ iQEcBAABAgAGBQJXYRjRAAoJEGEJLoW3InGJ3IwIAIY4SA6GxY3BjL60YyvsJPh/ HRCJwH+w7wt3Yc/9/bW2F+gF72kdHOOs2jfv+OZhq0q4OAN6fvVSczISY/82LpS7 DVdMQj2/YcHDT4xrDNBnXnviDO9G7am/9OE77kEbXrp7QPxvhjkicHNwy2rEflAA @@ -128,13 +144,13 @@ mergetag object 04b871796dc0420f8e7561a895b52484b701d51a type commit tag signedtag tagger C O Mitter 1465981006 +0000 - + $ signed tag - + $ signed tag message body -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 - + $ iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh 8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods -- cgit v1.2.3