feat(fish-deps): build fish from source via git + cargo when upgrading

Adds a git-cargo-fish install method that clones fish-shell, checks out
the latest tag, and runs `uv run --no-managed-python cargo install --path .`.
This is offered first in `fish-deps install` (requires cargo + uv) and
used automatically by `fish-deps update`, falling back to the system PM
when cargo or uv are absent.

Removes the stale `cargo install fish` README note (that crate is a
library, not the shell binary).

README.md

@@ -254,7 +254,10 @@ rm -f file.txt  # Falls through to standard rm -f
 | `fzf-update` | Install or upgrade fzf from git HEAD into `~/.fzf` (guarantees the latest build) |
 | `check_fish_deps` | Legacy alias — delegates to `fish-deps status` |
 
-Install method priority: **cargo** (for Rust tools, gets latest crate) → **system PM** (paru/apt/brew/etc.) → **git clone** (fzf) → **curl installer** (starship, fisher) → **pipx** (Python tools). When multiple methods are available for a tool, you are prompted to choose.
+Install method priority: **git+cargo source build** (fish) → **cargo** (other Rust tools, gets latest crate) → **system PM** (paru/apt/brew/etc.) → **git clone** (fzf) → **curl installer** (starship, fisher) → **pipx** (Python tools). When multiple methods are available for a tool, you are prompted to choose.
+
+> [!NOTE]
+> Upgrading Fish from source requires **cargo** and **[uv](https://docs.astral.sh/uv/)**. If either is missing, `fish-deps install`/`update` will fall back to the system package manager instead.
 
 ### Docker
 
@@ -502,11 +505,7 @@ Named context shortcuts (e.g. `dcr`, `dck`) live in `~/.config/.user-dots/fish/l
 
 > [!WARNING]
 > Fish **4.0 or newer is required.** This config uses `test` syntax and other constructs that are incompatible with Fish 3.x. Older versions will produce errors on startup.
-> If you are on an older Fish, you can upgrade via cargo (Fish 4.x is a Rust rewrite published to crates.io):
+> If you are on an older Fish, run `fish-deps install` or `fish-deps update` — it will build and install the latest Fish from source using git + cargo (requires cargo and uv).
-> ```
-> cargo install fish
-> ```
-> Or run `fish-deps update` once cargo is available — it will upgrade Fish via cargo automatically.
 
 ### Recommended
 

functions/_fish_deps_catalog.fish

@@ -10,7 +10,8 @@
 #   _fdc_cargo   — cargo crate name, or "" if not on crates.io
 #   _fdc_pm      — system PM package name, or "" if not in repos
 #   _fdc_special — special install key: rustup-installer | fisher-bootstrap |
-#                  fzf-update | paru-build | pipx | curl-installer | "" (none)
+#                  fzf-update | paru-build | pipx | curl-installer |
+#                  git-cargo-fish | "" (none)
 #
 # cargo is listed second so it is installed before Rust tools that depend on it.
 function _fish_deps_catalog
@@ -25,7 +26,7 @@ function _fish_deps_catalog
         rec rec rec rec rec rec rec rec rec rec rec rec rec rec
 
     set -g _fdc_cargo \
-        fish "" "" starship "" zoxide "" "" \
+        "" "" "" starship "" zoxide "" "" \
         "" "" \
         eza lsd bat "" du-dust "" "" "" ripgrep "" "" trashy "" ""
 
@@ -35,7 +36,7 @@ function _fish_deps_catalog
         eza lsd bat btop dust duf prettyping most ripgrep lazygit lazydocker trash kitty wezterm
 
     set -g _fdc_special \
-        "" rustup-installer fisher-bootstrap curl-installer fzf-update "" "" paru-build \
+        git-cargo-fish rustup-installer fisher-bootstrap curl-installer fzf-update "" "" paru-build \
         wakatime-binary "" \
         "" "" "" "" "" "" "" "" "" "" curl-lazydocker "" "" ""
 end

functions/_fish_deps_install.fish

@@ -47,6 +47,18 @@ function _fish_deps_install
 
             # Preferred special methods — listed before system PM so they are the default
             switch $special
+                case git-cargo-fish
+                    if type -q cargo; and type -q uv
+                        set -a methods special-git-cargo-fish
+                        set -a method_labels "build from source (git + cargo)"
+                    else
+                        set_color brblack
+                        set -l _need
+                        type -q cargo; or set -a _need cargo
+                        type -q uv; or set -a _need uv
+                        echo "  note: "(string join " and " $_need)" not found — install them first to build fish from source"
+                        set_color normal
+                    end
                 case rustup-installer
                     set -a methods special-rustup
                     set -a method_labels "rustup installer (curl | sh)"
@@ -194,6 +206,21 @@ function _fish_deps_install
                     and makepkg -si --noconfirm
                     and popd
                     rm -rf $_build_dir
+                case special-git-cargo-fish
+                    set -l _tmpdir (mktemp -d)
+                    set -l _build_ok 0
+                    git clone https://github.com/fish-shell/fish-shell "$_tmpdir"
+                    and begin
+                        set -l _tag (git -C "$_tmpdir" for-each-ref refs/tags/ --format '%(refname:short)' --sort=version:refname | tail -1)
+                        test -n "$_tag"; and git -C "$_tmpdir" checkout "$_tag"
+                        true
+                    end
+                    and pushd "$_tmpdir"
+                    and uv run --no-managed-python cargo install --path .
+                    and set _build_ok 1
+                    popd 2>/dev/null
+                    rm -rf "$_tmpdir"
+                    test $_build_ok -eq 1
                 case special-pipx
                     pipx install $bin
                 case special-pip

functions/_fish_deps_update.fish

@@ -93,6 +93,45 @@ function _fish_deps_update
             continue
         end
 
+        # fish: prefer build from source via git + cargo; fall back to PM
+        if test "$special" = git-cargo-fish
+            if type -q cargo; and type -q uv
+                echo "Updating $bin..."
+                set -l _tmpdir (mktemp -d)
+                set -l _build_ok 0
+                git clone https://github.com/fish-shell/fish-shell "$_tmpdir"
+                and begin
+                    set -l _tag (git -C "$_tmpdir" for-each-ref refs/tags/ --format '%(refname:short)' --sort=version:refname | tail -1)
+                    test -n "$_tag"; and git -C "$_tmpdir" checkout "$_tag"
+                    true
+                end
+                and pushd "$_tmpdir"
+                and uv run --no-managed-python cargo install --path .
+                and set _build_ok 1
+                popd 2>/dev/null
+                rm -rf "$_tmpdir"
+                if test $_build_ok -eq 1
+                    set updated_any 1
+                    set_color yellow
+                    echo "  Fish updated — restart your shell to use the new version."
+                    set_color normal
+                end
+            else if test -n "$pm_pkg"; and test -n "$pm"
+                echo "Updating $bin (cargo/uv unavailable, using system PM)..."
+                _fish_deps_pm_upgrade $pm_pkg
+                set updated_any 1
+                set_color yellow
+                echo "  Fish updated — restart your shell to use the new version."
+                set_color normal
+            else
+                set_color yellow
+                echo "  fish: cannot update — install cargo and uv to build from source"
+                set_color normal
+            end
+            set i (math $i + 1)
+            continue
+        end
+
         # curl-installer tools (starship etc.): re-run install script, which upgrades in place
         if test "$special" = curl-installer
             if test "$bin" = starship
@@ -109,11 +148,6 @@ function _fish_deps_update
             echo "Updating $bin..."
             cargo install --force $cargo_crate
             set updated_any 1
-            if test "$bin" = fish
-                set_color yellow
-                echo "  Fish updated — restart your shell to use the new version."
-                set_color normal
-            end
             set i (math $i + 1)
             continue
         end