Minitar incorrectly roundtrips files with very long filenames

[halostatue]

I recently discovered floj/minitar-lfn-problem illustrating an issue with minitar extraction of tarballs with very long filenames; it has never been reported as a bug. I have forked it as halostatue/minitar-lfn-problem and added an additional output because the diagnosis (missing files) is incorrect.

What is currently happening is worse because the files that are supposed to be missing are in fact mangled (that is, they are present, but they have been written to different locations than they should be). Comparing the extracted directories, we get this:

--- /var/folders/c6/k_j3j3w11590l8x6t8rwxw200000gn/T//.psub.N35VDqw9Zf	2024-08-11 12:03:28
+++ /var/folders/c6/k_j3j3w11590l8x6t8rwxw200000gn/T//.psub.CqZ7ky7GZ4	2024-08-11 12:03:28
@@ -30,7 +30,6 @@
 /k6hly56/mh/ri2pa1/04/ud6zm3nkjkls6ha1pqq81ptmg558psw33e8t32qsev.br
 /k6hly56/mh/ri2pa1/04/z5r3sv9isgut5tega9arqc146cna8.js
 /k6hly56/mh/ri2pa1/04/7b20zbxjqk834fd.js
-/k6hly56/mh/ri2pa1/04/5k8mnvwxe7hmvp1n932o4mn2b25gqrxfrbe4jfjbig6kzhphnsfkrtqruypfzl93u0ohlv9yyxcoxn6jg6iv5ml8e27jdqjiikyq3.js
 /k6hly56/mh/ri2pa1/04/nt3gzckca57gnnosgld6esjqi.br
 /k6hly56/mh/ri2pa1/04/8fpehrilj932d8twhwmxggcc7jufxr0ikycgw4hezmsqks5rkfnnxi80.map
 /k6hly56/mh/ri2pa1/04/r1x9nztj5zhh9wfijl97tg.js
@@ -45,39 +44,48 @@
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 /k6hly56/mh/ri2pa1/04/ztj1tjnysbi07xibqbzw82r9jb13b04l.gz
-/k6hly56/mh/ri2pa1/04/zregt5t93h8u9wc62q6o9368j78zfcavfcwb3h44p6ueaw95jsu8goeiatyxkozcwr452fqo4iqz3r2eldu8g1q93icccegzw0chny35.gz
 /k6hly56/mh/ri2pa1/04/qxgbaykcnn2gdrzocbvufeuujx56at7vhshny91lbq14jms8mchv.js
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-/k6hly56/mh/ri2pa1/04/tb3z3gmjkjmrzyomg7qz97fb7uxpc2s78hlu97gjqdgtzen0kdur28cmj12c2g2mlizviit6zpnmp32okqpx0a9nl8p5obzhrv2c5lse2z0gf8h.gz
 /k6hly56/mh/ri2pa1/04/4undrwj7kg9ugz0b8m8nclrkd1q64obgh3ya5u95v575wtrhx9oxq4rnrlr16djveaprtr6g2.map
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 /k6hly56/mh/ri2pa1/04/1y1kq8xw5pcjlzd4xgsyeom5488dq2hn27z8ptzh350s0wou.gz
@@ -87,7 +95,6 @@
 /k6hly56/mh/ri2pa1/04/65khbci5z35naa6pg1g93tv0b8u7jem33bht90o.js
 /k6hly56/mh/ri2pa1/04/gbnvvlvy8zqeyti7xnhs8q9bdxps4dk.gz
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-/k6hly56/mh/ri2pa1/04/0afdks3r6k1mbf64xzuwh5efkuxurro63rbckjssmz9mdratf6ayfduqpb0r9qxx2mgnrs0thi0ohh4qtfylfd6cd506zawwic0u3ec0iluu4myn.map
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@@ -101,15 +108,12 @@
 /k6hly56/mh/ri2pa1/04/y2h909f85lnj5ico69rhjhx4j.gz
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 /k6hly56/mh/ri2pa1/04/76oaddmvunzyujlpkg9kuny59a96.br
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 /k6hly56/mh/ri2pa1/04/palbewllu66smo9lj5dppwdysk9pdlyoc.map
 /k6hly56/mh/ri2pa1/04/9v7lsclu6pgtj1iq9vwjdyt8zfat5zsbl32sluawprf.map
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 /fjkornv7deyzvu9j0qc4j.sh
@@ -134,7 +138,6 @@
 /hpg5lfg/1j
 /hpg5lfg/1j/973e4t
 /hpg5lfg/1j/973e4t/hqc
-/hpg5lfg/1j/973e4t/hqc/rliudafdwjtth7uic5nm0pyf6w93qxa61gg810hnl93i5pats2dq5vt3uisguw5w58bcv8b4s2m4ey9pe8es0qiz2s1qefkll8tekn1sd.br
 /hpg5lfg/1j/973e4t/hqc/bui77tmck7icifwtu0ghgwtfyvshkcue0ets8062wxuw6xjp4pts1b9ppvgty8ak6odi2j9le40p4ql5tdfybq2srzobs9.gz
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@@ -146,12 +149,17 @@
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+/hpg5lfg/1j/973e4t/hqc/hpg5lfg
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+/hpg5lfg/1j/973e4t/hqc/hpg5lfg/1j/973e4t/hqc/rliudafdwjtth7uic5nm0pyf6w93qxa61gg810hnl93i5pats2dq5vt3uisguw5w58bcv8b4s2m4ey9pe8es0qiz2s1qefkll8tekn1sd.br
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 /hpg5lfg/1j/973e4t/hqc/0vzqtchg3lx5fcgngmm.gz

The most interesting part of that output is that the target directory structure is being duplicated:

+/k6hly56/mh/ri2pa1/04/k6hly56
+/k6hly56/mh/ri2pa1/04/k6hly56/mh
+/k6hly56/mh/ri2pa1/04/k6hly56/mh/ri2pa1
+/k6hly56/mh/ri2pa1/04/k6hly56/mh/ri2pa1/04

We can see that the files are being written to a duplicate tree inside the tree:

-/k6hly56/mh/ri2pa1/04/5k8mnvwxe7hmvp1n932o4mn2b25gqrxfrbe4jfjbig6kzhphnsfkrtqruypfzl93u0ohlv9yyxcoxn6jg6iv5ml8e27jdqjiikyq3.js
+/k6hly56/mh/ri2pa1/04/k6hly56/mh/ri2pa1/04/5k8mnvwxe7hmvp1n932o4mn2b25gqrxfrbe4jfjbig6kzhphnsfkrtqruypfzl93u0ohlv9yyxcoxn6jg6iv5ml8e27jdqjiikyq3.js

This was originally found with Minitar 0.9 but exists in Minitar 1.0.