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`builtins.fetchGit` weird behaviour
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fetchGit-weird-outputs.md

Some context at the very beginning:

[~/clones/leftpad]$ git log --pretty=oneline --all
db1442a0556c2b133627ffebf455a78a1ced64b9 (HEAD -> master, tag: v0.0.1, origin/master, origin/HEAD) chore(release): 0.0.1
2cc67dc48e3a60ee9702ad01ac932c3ae5565d28 test: Add test suite with jsverify
6d086b454204e570d78c3d8d005e1d14f0291635 Create license
80683e5129cc49e4508d095ed77e6ec1dea65e37 (origin/greenkeeper/initial) docs(readme): add Greenkeeper badge
6f334bd795c1184e4de837968e13cfbdcaae6bd3 Repo and fix
74fccbddc0e108cbafe9afa952ee5b7600ae1422 First

This is where I started experimenting with Nix issue #5128 in Nix 2.10.3:

nix-repl> builtins.fetchGit {
  ref = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  url = "https://github.com/tmcw/leftpad";
} 
fetching Git repository 'https://github.com/tmcw/leftpad'fatal: couldn't find remote ref refs/heads/db1442a0556c2b133627ffebf455a78a1ced64b9
error: program 'git' failed with exit code 128

using allRefs it works alright:

nix-repl> builtins.fetchGit {
  ref = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  url = "https://github.com/tmcw/leftpad";
  allRefs = true;
 }
warning: could not update mtime for file '/home/toraritte/.cache/nix/gitv3/0240dfgnkwmgqs7sma8rns8wlwxiv40b1lddl2sg2i0hnw7ym5c0/refs/heads/db1442a0556c2b133627ffebf455a78a1ced64b9': No such file or directory
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}

Then tried fetching the branches with and without allRefs, and the results were what was expected:

nix-repl> builtins.fetchGit { ref = "master"; url = "https://github.com/tmcw/leftpad"; }         
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "greenkeeper/initial"; url = "https://github.com/tmcw/leftpad
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "master"; url = "https://github.com/tmcw/leftpad"; allRefs = 
true;} 
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "greenkeeper/initial"; url = "https://github.com/tmcw/leftpad
"; allRefs = true; }
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

... and this is very it got weird when calling builtins.fetchGit only with url and allRefs:

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; allRefs = true; }         

warning: could not update mtime for file '/home/toraritte/.cache/nix/gitv3/0240dfgnkwmgqs7sma8rns8wlwxiv40b1lddl2sg2i0hnw7ym5c0/refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37': No such file or directory
fetching Git repository 'https://github.com/tmcw/leftpad'fatal: Refusing to point HEAD outside of refs/
warning: could not update cached head '80683e5129cc49e4508d095ed77e6ec1dea65e37' for 'https://github.com/tmcw/leftpad'
error: opening file '/home/toraritte/.cache/nix/gitv3/0240dfgnkwmgqs7sma8rns8wlwxiv40b1lddl2sg2i0hnw7ym5c0/refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37': No such file or directory

At this point I was trying random individual commits with and without allRefs, the results were again as expected:

nix-repl> builtins.fetchGit {
  url = "https://github.com/tmcw/leftpad";
  rev = "74fccbddc0e108cbafe9afa952ee5b7600ae1422";
}
{ lastModified = 1371605151;
  lastModifiedDate = "20130619012551";
  narHash = "sha256-+djyuUPJXNrQIQ1py4I7U3vrTq6RAtydzeORkEYRnLQ=";
  outPath = "/nix/store/4plgfa6hjb4ba13jmrz32ckyvgr8bwf1-source";
  rev = "74fccbddc0e108cbafe9afa952ee5b7600ae1422";
  revCount = 1;
  shortRev = "74fccbd";
  submodules = false;
}

nix-repl> builtins.fetchGit {
  url = "https://github.com/tmcw/leftpad";
  allRefs = true;
  rev = "74fccbddc0e108cbafe9afa952ee5b7600ae1422";
}
{ lastModified = 1371605151;
  lastModifiedDate = "20130619012551";
  narHash = "sha256-+djyuUPJXNrQIQ1py4I7U3vrTq6RAtydzeORkEYRnLQ=";
  outPath = "/nix/store/4plgfa6hjb4ba13jmrz32ckyvgr8bwf1-source";
  rev = "74fccbddc0e108cbafe9afa952ee5b7600ae1422";
  revCount = 1;
  shortRev = "74fccbd";
  submodules = false;
}

nix-repl> builtins.fetchGit {
  url = "https://github.com/tmcw/leftpad";
  allRefs = true;
  rev = "2cc67dc48e3a60ee9702ad01ac932c3ae5565d28";
}
{ lastModified = 1493781356;
  lastModifiedDate = "20170503031556";
  narHash = "sha256-Bal7zTLeH3bESQxywYFUHp3COhMOVWQv+/nqXS10i00=";
  outPath = "/nix/store/833i34wqr0silj472z4rwzryzan4axna-source";
  rev = "2cc67dc48e3a60ee9702ad01ac932c3ae5565d28";
  revCount = 4;
  shortRev = "2cc67dc";
  submodules = false;
}

nix-repl> builtins.fetchGit {
  url = "https://github.com/tmcw/leftpad";
  allRefs = true;
  rev = "2cc67dc48e3a60ee9702ad01ac932c3ae5565d28";
}
{ lastModified = 1493781356;
  lastModifiedDate = "20170503031556";
  narHash = "sha256-Bal7zTLeH3bESQxywYFUHp3COhMOVWQv+/nqXS10i00=";
  outPath = "/nix/store/833i34wqr0silj472z4rwzryzan4axna-source";
  rev = "2cc67dc48e3a60ee9702ad01ac932c3ae5565d28";
  revCount = 4;
  shortRev = "2cc67dc";
  submodules = false;
}

Then tried url and allRefs only, got an error, and then things got weird again:

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; allRefs = true; }                                                   
warning: could not update mtime for file '/home/toraritte/.cache/nix/gitv3/0240dfgnkwmgqs7sma8rns8wlwxiv40b1lddl2sg2i0hnw7ym5c0/refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37': No such fi
le or directory
fetching Git repository 'https://github.com/tmcw/leftpad'fatal: Refusing to point HEAD outside of refs/
warning: could not update cached head '80683e5129cc49e4508d095ed77e6ec1dea65e37' for 'https://github.com/tmcw/leftpad'
error: opening file '/home/toraritte/.cache/nix/gitv3/0240dfgnkwmgqs7sma8rns8wlwxiv40b1lddl2sg2i0hnw7ym5c0/refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37': No such file or directory

The issue here is that re-issued the same command from above of fetching branches with and without allRefs, and all call resulted in the exact same output:

The rev result 80683e5129cc49e4508d095ed77e6ec1dea65e37 is the HEAD of branch greenkeeper/initial.

nix-repl> builtins.fetchGit { ref = "master"; url = "https://github.com/tmcw/leftpad"; }                                                   
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "master"; url = "https://github.com/tmcw/leftpad"; allRefs = true; }
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "greenkeeper/initial"; url = "https://github.com/tmcw/leftpad"; }                      
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "greenkeeper/initial"; url = "https://github.com/tmcw/leftpad"; allRefs = true; }
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

Next, I was wondering if ref even matters at this point so tried out invalid references, and it sure didn't:

nix-repl> builtins.fetchGit { ref = "whatever"; url = "https://github.com/tmcw/leftpad"; }  
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { ref = "gibberish"; url = "https://github.com/tmcw/leftpad"; }
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

Then it didn't work simply by using URL:

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; }
fetching Git repository 'https://github.com/tmcw/leftpad'fatal: couldn't find remote ref refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37
error: program 'git' failed with exit code 128

Exited and then re-started the nix repl, tried out a couple of things, and after that fetching by only the URL worked again but the flaky behaviour remained. Maybe one should purge the ~/.cache directory?

$ nix repl
Welcome to Nix 2.10.3. Type :? for help.

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; }
fetching Git repository 'https://github.com/tmcw/leftpad'fatal: couldn't find remote ref refs/heads/80683e5129cc49e4508d095ed77e6ec1dea65e37
error: program 'git' failed with exit code 128

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; allRefs = true;}
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; }                
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; ref = "greenkeeper/initial";}  
{ lastModified = 1491858622;
  lastModifiedDate = "20170410211022";
  narHash = "sha256-8RO5tFUo/t8own92cdHiNzSZvzTLAvdo0rJHClvf1K0=";
  outPath = "/nix/store/7xc8hnzspar6f9g177m8ixh6x2cizrwl-source";
  rev = "80683e5129cc49e4508d095ed77e6ec1dea65e37";
  revCount = 3;
  shortRev = "80683e5";
  submodules = false;
}

nix-repl> builtins.fetchGit { url = "https://github.com/tmcw/leftpad"; }                             
{ lastModified = 1493781506;
  lastModifiedDate = "20170503031826";
  narHash = "sha256-0DbZHwAdvEUiHo3brZyyxw0WdNQOsQwGZZz4tboN3v8=";
  outPath = "/nix/store/8frq54wwgi63wqgkc7p6yrcljlx4zwzh-source";
  rev = "db1442a0556c2b133627ffebf455a78a1ced64b9";
  revCount = 5;
  shortRev = "db1442a";
  submodules = false;
}
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