add zig dep-hash command

[dweiller]

This PR adds the zig dep-hash command (called zig pkg-hash in #20180) for inspecting the dependency tree of a package.

> zig dep-hash --help
Usage: zig dep-hash [--list] [dep-name] [subdep...]

   List the hashes of packages in the build.zig.zon manifest.

Options:
  --graph                   Print dependency graph
  --list                    List all package hashes
  --build-root [path]       Set package root directory
  --global-cache-dir [path] Override the global cache directory
  -h, --help                Print this help and exit

What follows is a description of the current behaviour, for any bike-shedding/suggestions for alternative behaviour.

The command works solely off the build.zig.zons of a package and its transitive dependencies and doesn't perform any package fetching, so packages must already be present in the global cache to inspect their dependencies.

To get the hash of a (sub) dependency the name of the dependency (according to build.zig.zon) is given as a positional parameter with the name of sub-dependencies given as additional positional parameters. For example

> zig dep-hash mach mach_basisu basisu
1220da74ddbae5ccae5d0141e747023039488f266b98e7ceb860015f95b2dd10c650

prints the hash of the (third-level) sub-dependency basisu (this invocation walks the dependency tree root_pkg -> mach -> mach_basisu and gets the hash of basisu in the build.zig.zon of mach_basisu)

The --list flag can be provided to list the names and hashes of all dependencies instead of printing a single hash:

> zig dep-hash mach --list
mach_freetype           12206251ed342f400b80abf3c338521f5d8c83eb596899abf77a2afe0cfd46e61ff0
font_assets             12202b816e7c31c516bd87218fd56f9b1f93671e4ab42a2a98110d586c4b3bdd2730
mach_gpu_dawn           122060fbe61aa4a828002ca8949d9c3ef1b6b7ae3fa92558af7ccea7182e8d9d516c
mach_glfw               1220e5343c2fe2a490aa90dc52d92fd34ebfd7d0ffc7d246dd4720bb5c339ead4d7b
mach_objc               1220211475420584a552b461dd569f891d29cb8e9e485b97053be604680c8d6e2a3e
xcode_frameworks        12205d131983601cdb3500f38e9d8adaed5574fb0211b8b39291d2e9b90c6555ce59
direct3d_headers        12203594c3c97220742be1cc5343547bb25d8947e77bd52c50ef713da676d6f6d31f
opengl_headers          12209f5ec4fa073c3b5b5129a72b7b230596af48a732bed539e35161395ed590095d
vulkan_zig_generated    1220d2b6789b71a94e692cb2f060bff4ffa4edfe196216cd573da68e74ab884eb34e
linux_audio_headers     122042c20087cc1e40d24a61c9d725be36ac5914d6e87e1776cc3cfaecedbcc0be16
wayland_headers         1220f350a0782d20a6618ea4e2884f7d0205a4e9b02c2d65fe3bf7b8113e7860fadf
x11_headers             1220ddf168c855cf69b4f8c5284403106a3c681913e34453df10cc5a588d9bd1d005
zigimg                  1220dc313944ea71a87b4f54f26b1427ad2992a721a221cb42f7f80b8eee4e4944b7
mach_opus               12203e942ae6563c5fb05dff8e8a406b71fe6682342ae5d8d26093e6f9e3d2e02777
mach_example_assets     12204101e99906bee0fde5f82682bc822744a6f879dbf45374bebd92458492313df9

If a relative dependency it's path is displayed along with the annotation (local):

> zig dep-hash --list
zigimg     1220c0980dc05816b12a8188546b4847bcf38e5e99defc0ea79a8d6bd4809049a029
zig_wfc    1220ca5d40e299dd2e00396e13ecef043831d1438610a0c8f9246ec0c48ceee253f3
mach       12206c34197e552379b7b83b9b71e16230d3c87b5bff689f80d686b41b3486e9f486
nanovg     1220a6a2572713f2a29e54584b060ea19fd89b298bf89baf0b090b85a0a473527d4f
ztracy     vendor/ztracy (local)

The --graph flag can be provided to show the whole dependency graph of a package

> zig dep-hash --graph
RTD
├─ zigimg      1220c0980dc05816b12a8188546b4847bcf38e5e99defc0ea79a8d6bd4809049a029
├─ zig_wfc     1220ca5d40e299dd2e00396e13ecef043831d1438610a0c8f9246ec0c48ceee253f3
├─ mach        12206c34197e552379b7b83b9b71e16230d3c87b5bff689f80d686b41b3486e9f486
│  ├─ mach_freetype            12206251ed342f400b80abf3c338521f5d8c83eb596899abf77a2afe0cfd46e61ff0
│  │  ├─ freetype        1220babb7939707ca390b934657dfd3c8c3a6a78cc9442e4cbd43e3f9ffd49daec9e
│  │  │  └─ brotli     122059777e9e24227733f386b2929a78e15be9b748c99dba0d209744c910671b101c
│  │  ├─ harfbuzz        1220557b115b730afbece2ff4a073b6dc095d143318ba2f6b258cee13f580dd7e8ba
│  │  │  ├─ freetype     1220babb7939707ca390b934657dfd3c8c3a6a78cc9442e4cbd43e3f9ffd49daec9e (seen previously)
│  │  │  └─ brotli       122059777e9e24227733f386b2929a78e15be9b748c99dba0d209744c910671b101c (seen previously)
│  │  └─ font_assets     12202b816e7c31c516bd87218fd56f9b1f93671e4ab42a2a98110d586c4b3bdd2730
│  ├─ font_assets              12202b816e7c31c516bd87218fd56f9b1f93671e4ab42a2a98110d586c4b3bdd2730 (seen previously)
│  ├─ mach_gpu_dawn            122060fbe61aa4a828002ca8949d9c3ef1b6b7ae3fa92558af7ccea7182e8d9d516c
│  ├─ mach_glfw                1220e5343c2fe2a490aa90dc52d92fd34ebfd7d0ffc7d246dd4720bb5c339ead4d7b
│  ├─ mach_objc                1220211475420584a552b461dd569f891d29cb8e9e485b97053be604680c8d6e2a3e
│  ├─ xcode_frameworks         12205d131983601cdb3500f38e9d8adaed5574fb0211b8b39291d2e9b90c6555ce59
│  ├─ direct3d_headers         12203594c3c97220742be1cc5343547bb25d8947e77bd52c50ef713da676d6f6d31f
│  ├─ opengl_headers           12209f5ec4fa073c3b5b5129a72b7b230596af48a732bed539e35161395ed590095d
│  ├─ vulkan_zig_generated     1220d2b6789b71a94e692cb2f060bff4ffa4edfe196216cd573da68e74ab884eb34e
│  ├─ linux_audio_headers      122042c20087cc1e40d24a61c9d725be36ac5914d6e87e1776cc3cfaecedbcc0be16
│  ├─ wayland_headers          1220f350a0782d20a6618ea4e2884f7d0205a4e9b02c2d65fe3bf7b8113e7860fadf
│  ├─ x11_headers              1220ddf168c855cf69b4f8c5284403106a3c681913e34453df10cc5a588d9bd1d005
│  ├─ zigimg                   1220dc313944ea71a87b4f54f26b1427ad2992a721a221cb42f7f80b8eee4e4944b7
│  ├─ mach_opus                12203e942ae6563c5fb05dff8e8a406b71fe6682342ae5d8d26093e6f9e3d2e02777
│  └─ mach_example_assets      12204101e99906bee0fde5f82682bc822744a6f879dbf45374bebd92458492313df9
├─ nanovg      1220a6a2572713f2a29e54584b060ea19fd89b298bf89baf0b090b85a0a473527d4f
└─ ztracy      vendor/ztracy (local)
   └─ system_sdk     vendor/system-sdk (local)

Note that this prints the graph as a tree and will not re-print the subtree/subgraph of a dependency that has already been printed (note the '(seen previously)' annotations). This reduces the amount printed at the cost introducing some indirection (i.e. if you look at the second freetype line above, you'd have to scan upwards and find the prior occurrence of freetype to see that it depends on brotli). This is also a mitigation against the possibility of cycles in the dependency graph, which the compiler/build system currently allows (but doesn't handle robustly).

For convenience, when no positional parameters are given, the default behaviour is the same as --graph.

The --build-root flag can be used to specify the directory to operate on, rather than the current working directory (note that the usual search up parent directories will still happen when --build-root is provided, it just changes where the search starts from).

A minimum of four spaces are used to separate dependency names and hashes with --list, with extra spaces used in order to align the hashes. The alignment for --graph could probably use some work, it aligns hashes that are in the same manifest.