The problem seems to be some bad annotated tags with missing emails in their 'tagger' lines. For example:
git cat-file -p db3f12f432913395f01d3fbf21ddde61c3aa4ad8 object f8cb67a0b57b07610802435587f2d2311254d077 type commit tag alpha_0_6_1 tagger Sergey Poznyakoff Here are all the bad tags in this repo: rel_0_5 09fb4b0a70344ff0ce6be311bfdd9600cc0b2deb f7a02fd442854017348999bced3552f2041bc86f rel-1_0 0e5886c884afed8354f22ec046fa5ffc5e0c37e1 3facf5ecacfc326f04f011bf78bc33bf97a46abe rel_0_3_1 2b19d364a643f2eea20d1e3b0a87b288a1d6f984 c84cc5d63bef16f2dd318eba268f077367700ca5 mu-1-2-90-included-argp 2d814aa929aa5ffde116acc78894256e3e9f41b1 7e7a878f730f23533e2101ea88ae40cc9e204dff rel_0_1 306b6b35b9af77ee389cb5961ae17eb998c9c6b0 c0ab0f0ca83bc7fbb295714e334e039f99d57f84 rel_0_4 3e0b651559df5584f2e4b1c7c7fbdc90624288d3 d63c7846a2c4ba71209ee030a415402e3e82b8dd alpha_0_6_91 46cdd27e51cd0275665536a8952420fae28eff70 ea4dcf344a94aca38ddd1b7319b1b6194c2cbbf4 alpha_0_6_90 4e6d75a11fbad017ddf58f6c8052ac63e6dd4bf9 b93156813d1112dab689c697eb817e62bb73bbd5 rel_0_2 560cec7a60688f2628574598073ac9c1bb4a605e 8f8226a4cf20136997ab6eb070aa1dd281118c53 alpha_0_6_91_after_namespace 77dfb64e904e8d40215f9a51e433aedf0c3e18d1 16a6c59c10ebafa0004a6d6d9ad0561a5cfc1a11 alpha_0_6_92_before_mu_off_t 7cf75bef98046b15cbe85ebb25d42719e25b275d 94a921a76baa0de70ffe1b4175b51d3a8e969e04 alpha_0_6_91_libmailbox 7d45e91505800db42c39dd9c7a47582fa6a01d74 c3967af2ec322bf00095544b2952937ef1446162 alpha_0_6_92 7fe84731720b1f4303d18d7e287131a8e7fa4e86 50b24ab6ffd231be0c601f92ca3985eff2feeb8a rel_0_3 80982187eb0250500c9b016b5a47e4ced869126c 747036b72d4423302743ab4cec77831c5c987d69 mu-1-2-90-separate-argp-cfg afc50284c101446bb17e72ef96216b5a042e0915 0112e3c07a2b8fcfb642ace4b880575f86fcf933 mu-1-2-1-before-new-config b2a909aca40284b31faa753597bd7e46ec4c19fa a1dc0f56e3b24e7c042ea90f3ace824f156403c8 alpha_0_6_91_before_namespace b7e27bce5ccacfceb40f0924640fb7d22b92b9b1 ef22616eba2aaa4e05079852ac1fa67c4ceeff08 alpha_0_6_1 db3f12f432913395f01d3fbf21ddde61c3aa4ad8 f8cb67a0b57b07610802435587f2d2311254d077 alpha_0_6_95 e02aab6e2913c7188e0396de1b68bdb8ea07e44a f69c4bbf9ce09628798d38e10ae23e15e895b3ec mailutils-0-0-9 e908de58ef1a9faad6717cb4b98d1dc3ed446130 de632534b0552700c8c9dac4fcbfa8549466f5da release_1_1 ec9aa1f040a8e2886a94e8daf4558804a284494c a4d3de2482b8ff4c2e83deabb1bb2a7dfa36d5f3 rel_0_6 f544b7863b6b5f8c06023268012b68f836c97c72 997808e934d068897bd2ea3f599c211e9066b421 mu-1-2-90-included-gnulib fe68420022a22a448fe975f979a96039befeaabd e5d5ca6b39ee1f1e5c5aff255557649033a87698 A quick fix could be removing these old tags - they don't seem useful. Or we can fix them up and push the updated tags.
