Merge remote-tracking branch 'upstream/master' into path-info

Also improve content-address.hh API docs.

1 files changed, 30 insertions, 19 deletions

diff --git a/doc/manual/src/command-ref/env-common.md b/doc/manual/src/command-ref/env-common.md
index c5d38db47..bf00be84f 100644
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@@ -2,18 +2,29 @@
 
 Most Nix commands interpret the following environment variables:
 
-  - [`IN_NIX_SHELL`]{#env-IN_NIX_SHELL}\
+  - <span id="env-IN_NIX_SHELL">[`IN_NIX_SHELL`](#env-IN_NIX_SHELL)</span>\
     Indicator that tells if the current environment was set up by
     `nix-shell`. It can have the values `pure` or `impure`.
 
-  - [`NIX_PATH`]{#env-NIX_PATH}\
+  - <span id="env-NIX_PATH">[`NIX_PATH`](#env-NIX_PATH)</span>\
     A colon-separated list of directories used to look up the location of Nix
-    expressions using [paths](../language/values.md#type-path)
+    expressions using [paths](@docroot@/language/values.md#type-path)
     enclosed in angle brackets (i.e., `<path>`),
     e.g. `/home/eelco/Dev:/etc/nixos`. It can be extended using the
-    [`-I` option](./opt-common.md#opt-I).
+    [`-I` option](@docroot@/command-ref/opt-common.md#opt-I).
 
-  - [`NIX_IGNORE_SYMLINK_STORE`]{#env-NIX_IGNORE_SYMLINK_STORE}\
+    If `NIX_PATH` is not set at all, Nix will fall back to the following list in [impure](@docroot@/command-ref/conf-file.md#conf-pure-eval) and [unrestricted](@docroot@/command-ref/conf-file.md#conf-restrict-eval) evaluation mode:
+
+      1. `$HOME/.nix-defexpr/channels`
+      2. `nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs`
+      3. `/nix/var/nix/profiles/per-user/root/channels`
+
+    If `NIX_PATH` is set to an empty string, resolving search paths will always fail.
+    For example, attempting to use `<nixpkgs>` will produce:
+
+        error: file 'nixpkgs' was not found in the Nix search path
+
+  - <span id="env-NIX_IGNORE_SYMLINK_STORE">[`NIX_IGNORE_SYMLINK_STORE`](#env-NIX_IGNORE_SYMLINK_STORE)</span>\
     Normally, the Nix store directory (typically `/nix/store`) is not
     allowed to contain any symlink components. This is to prevent
     “impure” builds. Builders sometimes “canonicalise” paths by
@@ -35,58 +46,58 @@ Most Nix commands interpret the following environment variables:
 
     Consult the mount 8 manual page for details.
 
-  - [`NIX_STORE_DIR`]{#env-NIX_STORE_DIR}\
+  - <span id="env-NIX_STORE_DIR">[`NIX_STORE_DIR`](#env-NIX_STORE_DIR)</span>\
     Overrides the location of the Nix store (default `prefix/store`).
 
-  - [`NIX_DATA_DIR`]{#env-NIX_DATA_DIR}\
+  - <span id="env-NIX_DATA_DIR">[`NIX_DATA_DIR`](#env-NIX_DATA_DIR)</span>\
     Overrides the location of the Nix static data directory (default
     `prefix/share`).
 
-  - [`NIX_LOG_DIR`]{#env-NIX_LOG_DIR}\
+  - <span id="env-NIX_LOG_DIR">[`NIX_LOG_DIR`](#env-NIX_LOG_DIR)</span>\
     Overrides the location of the Nix log directory (default
     `prefix/var/log/nix`).
 
-  - [`NIX_STATE_DIR`]{#env-NIX_STATE_DIR}\
+  - <span id="env-NIX_STATE_DIR">[`NIX_STATE_DIR`](#env-NIX_STATE_DIR)</span>\
     Overrides the location of the Nix state directory (default
     `prefix/var/nix`).
 
-  - [`NIX_CONF_DIR`]{#env-NIX_CONF_DIR}\
+  - <span id="env-NIX_CONF_DIR">[`NIX_CONF_DIR`](#env-NIX_CONF_DIR)</span>\
     Overrides the location of the system Nix configuration directory
     (default `prefix/etc/nix`).
 
-  - [`NIX_CONFIG`]{#env-NIX_CONFIG}\
+  - <span id="env-NIX_CONFIG">[`NIX_CONFIG`](#env-NIX_CONFIG)</span>\
     Applies settings from Nix configuration from the environment.
     The content is treated as if it was read from a Nix configuration file.
     Settings are separated by the newline character.
 
-  - [`NIX_USER_CONF_FILES`]{#env-NIX_USER_CONF_FILES}\
+  - <span id="env-NIX_USER_CONF_FILES">[`NIX_USER_CONF_FILES`](#env-NIX_USER_CONF_FILES)</span>\
     Overrides the location of the user Nix configuration files to load
     from (defaults to the XDG spec locations). The variable is treated
     as a list separated by the `:` token.
 
-  - [`TMPDIR`]{#env-TMPDIR}\
+  - <span id="env-TMPDIR">[`TMPDIR`](#env-TMPDIR)</span>\
     Use the specified directory to store temporary files. In particular,
     this includes temporary build directories; these can take up
     substantial amounts of disk space. The default is `/tmp`.
 
-  - [`NIX_REMOTE`]{#env-NIX_REMOTE}\
+  - <span id="env-NIX_REMOTE">[`NIX_REMOTE`](#env-NIX_REMOTE)</span>\
     This variable should be set to `daemon` if you want to use the Nix
     daemon to execute Nix operations. This is necessary in [multi-user
-    Nix installations](../installation/multi-user.md). If the Nix
+    Nix installations](@docroot@/installation/multi-user.md). If the Nix
     daemon's Unix socket is at some non-standard path, this variable
     should be set to `unix://path/to/socket`. Otherwise, it should be
     left unset.
 
-  - [`NIX_SHOW_STATS`]{#env-NIX_SHOW_STATS}\
+  - <span id="env-NIX_SHOW_STATS">[`NIX_SHOW_STATS`](#env-NIX_SHOW_STATS)</span>\
     If set to `1`, Nix will print some evaluation statistics, such as
     the number of values allocated.
 
-  - [`NIX_COUNT_CALLS`]{#env-NIX_COUNT_CALLS}\
+  - <span id="env-NIX_COUNT_CALLS">[`NIX_COUNT_CALLS`](#env-NIX_COUNT_CALLS)</span>\
     If set to `1`, Nix will print how often functions were called during
     Nix expression evaluation. This is useful for profiling your Nix
     expressions.
 
-  - [`GC_INITIAL_HEAP_SIZE`]{#env-GC_INITIAL_HEAP_SIZE}\
+  - <span id="env-GC_INITIAL_HEAP_SIZE">[`GC_INITIAL_HEAP_SIZE`](#env-GC_INITIAL_HEAP_SIZE)</span>\
     If Nix has been configured to use the Boehm garbage collector, this
     variable sets the initial size of the heap in bytes. It defaults to
     384 MiB. Setting it to a low value reduces memory consumption, but
@@ -103,4 +114,4 @@ New Nix commands conform to the [XDG Base Directory Specification], and use the
 Classic Nix commands can also be made to follow this standard using the [`use-xdg-base-directories`] configuration option.
 
 [XDG Base Directory Specification]: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
-[`use-xdg-base-directories`]: ../command-ref/conf-file.md#conf-use-xdg-base-directories
\ No newline at end of file
+[`use-xdg-base-directories`]: @docroot@/command-ref/conf-file.md#conf-use-xdg-base-directories
\ No newline at end of file