(cherry picked from commit e2fc575)

Cherry-pick "Use fragment size for autoGC capacity calculation" on 2.3

…path

Reported by Kane York.

(cherry picked from commit 2292814)

Fixes #3906.

(cherry picked from commit 59067f0)

…port

repl.cc: Check for HAVE_BOEHMGC

This doesn't just cause problems for nix-store --serve but also results
in certain build failures. Builds that use unix domain sockets in their
tests often fail because the /var/folders prefix already consumes more
than half of the maximum length of socket paths.

    struct sockaddr_un {
       sa_family_t sun_family;               /* AF_UNIX */
       char        sun_path[108];            /* Pathname */
    };

(cherry picked from commit 4d9db42)

never use /var/folders for TMPDIR on darwin (2.3 backport)

Observed on Centos 7 when user namespaces are disabled:
DerivationGoal::startBuilder() throws an exception, ~DerivationGoal()
waits for the child process to exit, but the child process hangs
forever in drainFD(userNamespaceSync.readSide.get()) in
DerivationGoal::runChild(). Not sure why the SIGKILL doesn't get
through.

Issue #4092.

(cherry picked from commit d761485)

Fixes #1560, #2377.

(cherry picked from commit 924712e)

Keeping this commit narrow for reviewability, but some of these
conditionals will change in subsequent commits in this PR.

Fixes #3852.

(cherry picked from commit 9c3dc9d)
Signed-off-by: Domen Kožar <domen@dev.si>

- xpath -> xmllint: xpath's cli interface changed in Big Sur
  rather than add conditional logic for picking the correct
  syntax for xpath, I'm changing to xmllint --xpath, which
  appears to be consistent across versions I've tested...

- /plist/dict/key[text()='Writable']/following-sibling::true[1]
  doesn't do quite what's expected. It was written to try to
  select a <true /> node paired with the Writable key, but it
  will also select the *next* <true /> node that appears even
  if it was paired with another key.

- I think there's also a logic bug in the conditionals here.
  I'm not sure anyone ever actuall saw it, thanks to the xpath
  bug, though. With the xpath fix, this conditional passes if /nix
  does not exist, / IS writable, and the version is Catalina+.

  I think it meant to test for /nix does not exist, / is NOT
  writable, and the version is Catalina+. I reworked this lightly
  to make it a little clearer at the code level.

(cherry picked from commit 1f02b65)
Signed-off-by: Domen Kožar <domen@dev.si>

As mentioned in previous commit, Big Sur changes the syntax for the
xpath command slightly.

In the process of testing out replacements for these, I noticed a few
small simplification wins.

(cherry picked from commit e736f8f)
Signed-off-by: Domen Kožar <domen@dev.si>

Fixes #3957. Just runs both forms to minimize moving parts.

(cherry picked from commit fe80790)
Signed-off-by: Domen Kožar <domen@dev.si>

Mac OS multi-user installations are currently broken because all requests
made by nix-daemon to the binary cache fail with:

```
unable to download ... Problem with the SSL CA cert (path? access rights?) (77).
```

This change ensures that the nix-daemon knows where to find the SSL CA cert file.

Fixes #2899 and #3261.

(cherry picked from commit b7c0223)