docs: reorder readme content

Sentence case for the headings, Django, Docker, Git and Rust where the
product is meant rather than the command, and SQL and URL as initialisms.
The role names `ahab status` prints stay lowercase, being names.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DFPds8Do63ZSRMwZ3guDyg

Cargo.lock

@@ -4,7 +4,7 @@ version = 4
 
 [[package]]
 name = "ahab"
-version = "0.4.2"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "clap",

README.md

@@ -1,20 +1,140 @@
 # ahab
 
-A wrapper around `docker compose` for our dockerized django projects, so the
+A wrapper around `docker compose` for our dockerized Django projects, so the
 same commands work in every repository.
 
-## installing
+It reads `docker compose config` to work out which service runs Django and
+which one is the database, so nothing here takes a service name or a `-f`.
+Everything it does, it does by running `docker`, `git` and the Postgres tools.
+
+## Installing
+
+You will need Rust installed. Clone the repo and run:
 
-You will need rust installed. Clone repo and run:
 ```bash
 cargo install --path .
 ```
 
-## what it makes of a project
+## Django
 
-`ahab status` prints the services it picked, the containers behind them, the
-credentials it would use and what the store holds, reporting whatever it cannot
-work out rather than stopping at the first thing:
+Each of these runs `docker compose run --rm` against the Django service, so it
+goes through the image's own entrypoint:
+
+```bash
+ahab django run <cmd>                # anything, in a fresh container
+ahab django bash                     # a shell in a fresh container
+ahab django manage <args>            # manage.py
+ahab django makemigrations
+ahab django migrate <args>
+ahab django shell
+ahab django make-command <app> <name>
+```
+
+## Postgres
+
+```bash
+ahab postgres dump <path>             # pg_dump, custom format
+ahab postgres dump -F plain <path>    # pg_dump, plain SQL
+ahab postgres dump -F tar <path>      # pg_dump, tar
+ahab postgres dump -F directory <d>   # pg_dump, a directory of files
+ahab postgres dump -F cluster <path>  # pg_dumpall, roles and all databases
+ahab postgres dump -F plain -z <path> # any of them, gzipped
+ahab postgres import <path>           # drop, create, then restore
+ahab postgres psql <args>             # psql in the database container
+```
+
+Dumps are written `0600`, under a name of their own until they are complete and
+then renamed over the target.
+
+Arguments reach `psql` untouched, and Docker is only asked for a terminal when
+there is one to hand over, so both of these work:
+
+```bash
+ahab postgres psql                          # interactive
+ahab postgres psql -tAc 'select count(*) from auth_user' | wc -l
+```
+
+### What an import makes of a dump
+
+The shape is read from the file rather than from its name:
+
+- a `PGDMP` or `toc.dat` header — an archive, restored with `pg_restore`, as is
+  a directory produced by `pg_dump -Fd`
+- a `pg_dumpall` header — a whole cluster, which creates its own databases and
+  carries role statements, so the database is dropped but not recreated and the
+  dump goes to `psql` connected to `postgres`
+- gzip magic — decompressed on the way in, whichever of the three is inside
+- anything else — SQL, fed to `psql` with `ON_ERROR_STOP` and
+  `--single-transaction`, so a bad file rolls back instead of half applying
+
+A cluster restore runs without `ON_ERROR_STOP`, so the expected complaints
+about roles that already exist do not stop it. Any other error fails the
+import. Importing into a cluster that has never held the database works either
+way.
+
+Containers are stopped before an import starts, so one that fails leaves the
+project stopped and says so.
+
+## Link
+
+A sandbox that mounts the repository can read anything untracked sitting in it
+— a `.env`, a dump, a key. Those paths can be moved out to a store of ahab's
+own and symlinked back: the host resolves the link, the sandbox does not.
+
+```bash
+ahab link add .env secrets/         # move out, leave symlinks behind
+ahab link restore .env              # move it back into the repository
+ahab link restore --all             # everything this repo has linked
+ahab link list                      # what the store holds for this repository
+ahab link check                     # what a sandbox can still read
+ahab link check --porcelain         # `<code> <path>`, for scripts
+ahab link check --exit-code         # exit 4 when anything is outside the store
+```
+
+Restoring is the inverse of adding: the file comes back to where it was and the
+store keeps nothing. A second checkout linking the same path is left with a
+dangling symlink, there being only ever one stored copy.
+
+Every stored path is in one of three states:
+
+```
+$ ahab link list
+store: /home/you/.local/share/ahab/git.aflabs.org/urnik/afurnik
+	linked:    .env
+	shadowed:  config.local.py
+	missing:   secrets/token
+```
+
+- `linked` — the symlink is there and points at the store
+- `shadowed` — a real file took the path back, so nothing reads the stored copy
+- `missing` — the symlink is gone, and nothing reads the stored copy either
+
+Only a linked path can be moved back, so `restore --all` says how many it left
+alone.
+
+Adding refuses two kinds of path:
+
+- **a tracked path**, which git would restore anyway. Where one is a symlink
+  leading out of the repository, `check` reports it under the code `T>`
+- **a symlink already leading out of the repository**, since moving it would
+  move the pointer and leave the contents where they are
+
+For scripts there is `--porcelain`, and `-z` for filenames that need it:
+entries end with a NUL, and the two paths of a symlink leading elsewhere are
+separated by one as well, the way `git status -z` reports a rename.
+
+The store lives under
+`${XDG_DATA_HOME:-$HOME/.local/share}/ahab/<host>/<owner>/<repo>/`, derived
+from the Git `origin` remote, or `_local/<checkout>` when there is no remote to
+name it after. Its directories are created `0700`. A remote or checkout name
+that needed characters replacing carries a short fingerprint of the original,
+so two of them cannot share a directory.
+
+## What ahab makes of your project
+
+Running `ahab status` prints the services it picked, the containers behind
+them, the credentials it would use and what the store holds. It reports
+whatever it cannot work out rather than stopping at the first problem:
 
 ```
 $ ahab status
@@ -30,12 +150,14 @@ store: /home/you/.local/share/ahab/git.aflabs.org/urnik/afurnik
 	`ahab link check` lists what a sandbox can still read
 ```
 
-## seeing what it runs
+## Seeing what it runs
 
-`-v` prints each docker command as it runs, `--dry-run` prints the ones it would
-run without running them, and `-q` prints only what was asked for, dropping the
-progress along the way (compose's own progress included). All work before or
-after the subcommand.
+- `-v` — print each Docker command as it runs
+- `--dry-run` — print the commands it would run, without running them
+- `-q` — print only what was asked for, dropping the progress along the way,
+  Compose's own included
+
+All three work before or after the subcommand:
 
 ```bash
 ahab -v django migrate
@@ -43,30 +165,50 @@ ahab --dry-run postgres import ./dump
 ahab -q postgres dump ./dump
 ```
 
-Nothing is written under `--dry-run`, filesystem included: `link add` and
+Nothing is written under `--dry-run`, the filesystem included: `link add` and
 `django make-command` say what they would do and leave the tree alone.
 
-## exit codes
+## Service detection
 
-- `0` — it ran and had nothing to report
-- `1` — it could not finish
-- `2` — the arguments were wrong
-- `4` — it ran fine and found something worth reporting, i.e.
-  `link check --exit-code` with anything outside the store
+Services can be named anything; ahab matches on what they are:
 
-## shell completion
+- **postgres** — the service whose image is a Postgres flavour, matching
+  `postg`, `timescale`, `pgvector` or `citus`
+- **django** — the service that both builds an image and sets
+  `DJANGO_SETTINGS_MODULE`. Where more than one does, a worker beside the web
+  service say, the one publishing ports wins
 
-`ahab completions <shell>` writes a completion script to stdout, for bash,
-elvish, fish, powershell or zsh:
+If nothing matches, or two candidates cannot be told apart, ahab says so and
+lists the services it looked at rather than guessing.
+
+The role and database come from `POSTGRES_USER` and `POSTGRES_DB` on the
+detected service, falling back to `db` when neither is set. Both have to be
+names: a value holding an `=`, a URL or a leading dash is refused, libpq
+reading such a name as a whole connection string.
+
+## The compose file
+
+Compose finds its own file and ahab does not pass `-f`, so set Docker's own
+`COMPOSE_FILE` when the file is not in the working directory, including its
+`base.yaml:override.yaml` form. A project's `.env` is a good place for it,
+since Docker reads that too:
+
+```
+COMPOSE_FILE=docker/docker-compose.yaml
+```
+
+## Shell completion
+
+Completion scripts are written to stdout, for Bash, Elvish, Fish, PowerShell
+or Zsh:
 
 ```bash
 ahab completions zsh > ~/.local/share/zsh/completions/_ahab
 eval "$(ahab completions zsh)"      # or one line in .zshrc, never goes stale
 ```
 
-Completions are also generated during the build. They land in
-`target/*/build/*/out/` by default, and `SHELL_COMPLETIONS_DIR_<SHELL>`
-installs a single shell's file straight into place:
+They are generated during the build as well, landing in
+`target/*/build/*/out/`. To install a single shell's file straight into place:
 
 ```bash
 SHELL_COMPLETIONS_DIR_ZSH=~/.local/share/zsh/completions \
@@ -74,170 +216,20 @@ SHELL_COMPLETIONS_DIR_FISH=~/.config/fish/completions \
   cargo install --path .
 ```
 
-`SHELL_COMPLETIONS_DIR` writes every shell into one directory instead.
+Set `SHELL_COMPLETIONS_DIR` to write every shell into one directory instead.
+Either way the path has to be absolute.
 
-## the compose file
+## Exit codes
 
-`ahab` does not pass `-f`. docker compose finds the file itself, so set
-docker's own `COMPOSE_FILE` when it is not in the working directory, including
-its `base.yaml:override.yaml` form. A project's `.env` is a good place for it,
-since docker reads that too:
+- `0` — it ran and had nothing to report
+- `1` — it could not finish
+- `2` — the arguments were wrong
+- `4` — it ran fine and found something worth reporting, which today means
+  `link check --exit-code` with anything outside the store
 
-```
-COMPOSE_FILE=docker/docker-compose.yaml
-```
+## Environment variables
 
-## service detection
-
-`ahab` finds the services it needs in `docker compose config`, so they can be
-named anything:
-
-- **postgres**: the service whose image is a postgres flavour, matching
-  `postg`, `timescale`, `pgvector` or `citus`
-- **django**: the service that both builds an image and sets
-  `DJANGO_SETTINGS_MODULE`. Where more than one does — a worker beside the web
-  service, say — the one publishing ports wins
-
-If nothing matches, or two candidates cannot be told apart, `ahab` says so and
-lists the services it looked at rather than guessing. Two services that both
-build and set the settings module are ambiguous unless exactly one of them
-publishes ports.
-
-`POSTGRES_USER` and `POSTGRES_DB` are read off the detected postgres service, so
-`dropdb`, `createdb`, `pg_restore` and `pg_dump` use the role and database the
-project declares, falling back to `db` when it declares neither. Both have to
-be names: `ahab` hands them to those tools as a role and a database, and libpq
-reads a database name holding an `=` or a url as a whole connection string,
-which would send a dump to whatever server it names. A value that could be read
-as something other than a name is refused rather than passed on.
-
-## django
-
-```bash
-ahab django run <cmd>                # in a fresh container, through the entrypoint
-ahab django bash                     # shell in a fresh container
-ahab django manage <args>            # manage.py
-ahab django makemigrations
-ahab django migrate <args>
-ahab django shell
-ahab django make-command <app> <name>
-```
-
-There is no `ahab django test`: which runner a project uses is the project's
-choice, and `manage.py test` exits 0 having collected nothing when the tests are
-written for pytest, so a wrong guess reads as a pass. Name the runner instead:
-
-```bash
-ahab django run pytest -x tests/
-```
-
-## postgres
-
-```bash
-ahab postgres dump <path>            # pg_dump, custom format
-ahab postgres dump -F plain <path>   # pg_dump, plain sql
-ahab postgres dump -F tar <path>     # pg_dump, tar
-ahab postgres dump -F directory <d>  # pg_dump, a directory of files
-ahab postgres dump -F cluster <path> # pg_dumpall, roles and all databases
-ahab postgres dump -F plain -z <path> # any of them, gzipped
-ahab postgres import <path>          # drop, create, then restore
-ahab postgres psql <args>            # psql in the database container
-```
-
-A dump is written `0600` and under a name of its own until it is complete, then
-renamed over the target: a cluster dump carries every role's password hash, and
-the default `0644` would hand it to anyone else with an account on the machine.
-
-`psql` passes its arguments through and only asks docker for a terminal when it
-has one to hand over, so both of these work:
-
-```bash
-ahab postgres psql                          # interactive
-ahab postgres psql -tAc 'select count(*) from auth_user' | wc -l
-```
-
-The format of a dump being imported is read from the file rather than its name.
-A custom format dump starts with `PGDMP` and a tar one with `toc.dat`, both of
-which go to `pg_restore`, as does a directory produced by `pg_dump -Fd`.
-Anything else is treated as sql and fed to `psql` with `ON_ERROR_STOP` and
-`--single-transaction`, so a bad file rolls back instead of half applying.
-A whole cluster dump from `pg_dumpall` is recognised by its header and handled
-differently again: it creates its own databases and carries role statements, so
-the database is dropped but not recreated, the dump goes to `psql` connected to
-`postgres`, and it runs without `ON_ERROR_STOP` because roles that already exist
-report errors that are expected. Any error it does not expect is reported and
-fails the import, since psql without `ON_ERROR_STOP` exits 0 having applied
-only part of the dump. Gzipped dumps are decompressed on the way in, whichever
-of the three they hold. A cluster that has never held the database yet is a
-valid target either way, so importing into a fresh one works.
-
-`import` stops the project before it starts, so an import that fails leaves it
-stopped and says so: `docker compose up` brings it back.
-
-## link
-
-`ahab link` moves untracked paths out of the repository into an out-of-repo
-store and symlinks them back, so a sandbox that mounts the repository sees a
-dangling symlink instead of the contents, while the host resolves it as before.
-
-```bash
-ahab link add .env secrets/         # move out, leave symlinks behind
-ahab link restore .env              # move it back into the repository
-ahab link restore --all             # everything this repo has linked
-ahab link list                      # what the store holds for this repository
-ahab link check                     # what a sandbox can still read
-ahab link check --porcelain         # `<code> <path>`, for scripts
-ahab link check --exit-code         # exit 4 when anything is outside the store
-```
-
-`restore` is the inverse of `add`: the file moves out of the store and back to
-where it was, and the store keeps nothing. A second checkout linking the same
-path is left with a dangling symlink, since there is only ever one stored copy.
-
-`list` says what state each stored path is in, which `check` cannot see because
-it asks git about the repository rather than reading the store:
-
-```
-$ ahab link list
-store: /home/you/.local/share/ahab/git.aflabs.org/urnik/afurnik
-	linked:    .env
-	shadowed:  config.local.py
-	missing:   secrets/token
-```
-
-`missing` is a path whose symlink is gone, `shadowed` one that a real file took
-back; either way the stored copy is the one nobody reads.
-
-`restore --all` moves back the linked ones and says how many it left, since
-there is nothing to undo for a path whose symlink is gone.
-
-`-z` is the porcelain format for scripts that must survive any filename: entries
-end with a NUL, and the two paths of a symlink leading elsewhere are separated
-by one as well, the way `git status -z` reports a rename.
-
-`check` looks at tracked paths too, since git tracks symlinks and one can lead
-out of the repository without appearing in any untracked listing. `add` cannot
-externalize a tracked path, so all `check` can do is report it, under the code
-`T>`.
-
-A symlink already leading out of the repository is not something `add` will
-take: moving the link would move the pointer and leave the contents where they
-are, so the store would hold a way back out while `check`, seeing a link into
-the store, called the repository clean.
-
-The store lives under
-`${XDG_DATA_HOME:-$HOME/.local/share}/ahab/<host>/<owner>/<repo>/`, derived
-from the git `origin` remote, or `_local/<checkout>` when there is no remote to
-name it after. Its directories are created `0700`: it exists to hold what
-should not be readable from the repository, and on a shared machine the default
-`0755` would leave that to whoever else has an account. A store path derived
-from a remote, or a checkout name, that needed characters replacing carries a
-short fingerprint of the original, so two of them cannot land on one directory.
-
-## configuration
-
-Currently `ahab` respects the following environment variables.
-
-- `AHAB_LINK_ROOT`: where `ahab link` keeps its store - the same as `--store`,
-  which takes precedence, and defaults to `${XDG_DATA_HOME:-$HOME/.local/share}/ahab`.
-  `ahab status` reads it too, so it reports the store the link commands use
+- `AHAB_LINK_ROOT` — where `ahab link` keeps its store, the same as `--store`,
+  which takes precedence. Defaults to
+  `${XDG_DATA_HOME:-$HOME/.local/share}/ahab`. Read by `ahab status` too, so it
+  reports the store the link commands actually use