Split nix-env and nix-store documentation per-subcommand

Documentation on "classic" commands with many sub-commands are
notoriously hard to discover due to lack of overview and anchor links.
Additionally the information on common options and environment variables
is not accessible offline in man pages, and therefore often overlooked
by readers.

With this change, each sub-command of nix-store and nix-env gets its
own page in the manual (listed in the table of contents), and each own
man page.

Also, man pages for each subcommand now (again) list common options
and environment variables. While this makes each page quite long and
some common parameters don't apply, this should still make it easier
to navigate as that additional information was not accessible on the
command line at all.

It is now possible to run 'nix-store --<subcommand> --help` to display
help pages for the given subcommand.

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

1 files changed, 38 insertions, 0 deletions

diff --git a/doc/manual/src/command-ref/nix-store/read-log.md b/doc/manual/src/command-ref/nix-store/read-log.md
new file mode 100644
index 000000000..4a88e9382
--- /dev/null
+++ b/doc/manual/src/command-ref/nix-store/read-log.md
@@ -0,0 +1,38 @@
+# Name
+
+`nix-store --read-log` - print build log
+
+# Synopsis
+
+`nix-store` {`--read-log` | `-l`} *paths…*
+
+# Description
+
+The operation `--read-log` prints the build log of the specified store
+paths on standard output. The build log is whatever the builder of a
+derivation wrote to standard output and standard error. If a store path
+is not a derivation, the deriver of the store path is used.
+
+Build logs are kept in `/nix/var/log/nix/drvs`. However, there is no
+guarantee that a build log is available for any particular store path.
+For instance, if the path was downloaded as a pre-built binary through a
+substitute, then the log is unavailable.
+
+{{#include ./opt-common.md}}
+
+{{#include ../opt-common.md}}
+
+{{#include ../env-common.md}}
+
+# Example
+
+```console
+$ nix-store -l $(which ktorrent)
+building /nix/store/dhc73pvzpnzxhdgpimsd9sw39di66ph1-ktorrent-2.2.1
+unpacking sources
+unpacking source archive /nix/store/p8n1jpqs27mgkjw07pb5269717nzf5f8-ktorrent-2.2.1.tar.gz
+ktorrent-2.2.1/
+ktorrent-2.2.1/NEWS
+...
+```
+