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Provide a more meaningful error-message for builtins.fetchGit if a revision can't be checked out

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A common pitfall when using e.g. `builtins.fetchGit` is the `fatal: not
a tree object`-error when trying to fetch a revision of a git-repository
that isn't on the `master` branch and no `ref` is specified.

In order to make clear what's the problem, I added a simple check
whether the revision in question exists and if it doesn't a more
meaningful error-message is displayed:

```
nix-repl> builtins.fetchGit { url = "https://github.com/owner/myrepo"; rev = "<commit not on master>"; }
moderror: --- Error -------------------------------------------------------------------- nix
Cannot find Git revision 'bf1cc5c648e6aed7360448a3745bb2fe4fbbf0e9' in ref 'master' of repository 'https://gitlab.com/Ma27/nvim.nix'! Please make sure that the rev exists on the ref you've specified or add allRefs = true; to fetchGit.
```

Closes #2431
This commit is contained in:
Maximilian Bosch 2020-07-14 20:59:24 +02:00
parent 9fab14adbc
commit 629af83b2d
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1 changed files with 22 additions and 0 deletions
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22
src/libfetchers/git.cc
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@ -392,6 +392,28 @@ struct GitInputScheme : InputScheme
AutoDelete delTmpDir(tmpDir, true);
PathFilter filter = defaultPathFilter;
RunOptions checkCommitOpts(
"git",
{ "-C", repoDir, "cat-file", "commit", input.getRev()->gitRev() }
);
checkCommitOpts.searchPath = true;
checkCommitOpts.mergeStderrToStdout = true;
auto result = runProgram(checkCommitOpts);
if (WEXITSTATUS(result.first) == 128
&& result.second.find("bad file") != std::string::npos
) {
throw Error(
"Cannot find Git revision '%s' in ref '%s' of repository '%s'! "
"Please make sure that the " ANSI_BOLD "rev" ANSI_NORMAL " exists on the "
ANSI_BOLD "ref" ANSI_NORMAL " you've specified or add " ANSI_BOLD
"allRefs = true;" ANSI_NORMAL " to " ANSI_BOLD "fetchGit" ANSI_NORMAL ".",
input.getRev()->gitRev(),
*input.getRef(),
actualUrl
);
}
if (submodules) {
Path tmpGitDir = createTempDir();
AutoDelete delTmpGitDir(tmpGitDir, true);