chore: update coderv2 dependency to 2.26.5 (#487)

Author: johnstcn

README.md

@@ -101,20 +101,5 @@ Issue: [#113](https://github.com/coder/envbuilder/issues/113)
 
 ## Contributing
 
-Building `envbuilder` currently **requires** a Linux system.
-
-On macOS or Windows systems, we recommend using a VM or the provided `.devcontainer` for development.
-
-**Additional Requirements:**
-
-- `go 1.22`
-- `make`
-- Docker daemon (for running tests)
-
-**Makefile targets:**
-
-- `build`: Builds and tags `envbuilder:latest` for your current architecture.
-- `develop`: Runs `envbuilder:latest` against a sample Git repository.
-- `test`: Runs tests.
-- `test-registry`: Stands up a local registry for caching images used in tests.
-- `docs/env-variables.md`: Updated the [environment variables documentation](./docs/env-variables.md).
+See [Development](./docs/development.md) for build instructions, dependency
+management notes, and common troubleshooting.

docs/development.md

@@ -0,0 +1,120 @@
+# Development
+
+Building envbuilder currently **requires** a Linux system.
+
+On macOS or Windows systems, we recommend using a VM or the provided
+`.devcontainer` for development.
+
+## Requirements
+
+- Go (see the version in `go.mod`)
+- `make`
+- Docker daemon (for running tests)
+
+## Makefile targets
+
+- `build`: Builds and tags `envbuilder:latest` for your current architecture.
+- `develop`: Runs `envbuilder:latest` against a sample Git repository.
+- `test`: Runs tests.
+- `test-registry`: Stands up a local registry for caching images used in tests.
+- `docs/env-variables.md`: Updates the environment variables documentation.
+
+## Dependency management
+
+Envbuilder has several forked and interrelated dependencies that require care
+when upgrading. This section documents known constraints and pitfalls.
+
+### Kaniko
+
+Envbuilder uses a [fork of Kaniko](https://github.com/coder/kaniko) for
+container image building. The replace directive in `go.mod` points to this fork:
+
+```
+replace github.com/GoogleContainerTools/kaniko => github.com/coder/kaniko <version>
+```
+
+The Kaniko fork pins its own versions of `docker/docker`,
+`containerd/containerd`, and related packages. When upgrading deps, be aware
+that the versions resolved by Go's MVS (minimum version selection) may be higher
+than what the Kaniko fork expects if other dependencies (like `coder/coder/v2`)
+require newer versions.
+
+### Tailscale
+
+Envbuilder uses a [Coder fork of Tailscale](https://github.com/coder/tailscale)
+via a replace directive:
+
+```
+replace tailscale.com => github.com/coder/tailscale <version>
+```
+
+The `coder/coder/v2` module depends on symbols that only exist in this fork
+(e.g. `netns.SetCoderSoftIsolation`, `tsaddr.CoderServiceIPv6`). When upgrading
+`coder/coder/v2`, you **must** also update the Tailscale replace to match the
+version used in `coder/coder/v2`'s own `go.mod`. You can find it with:
+
+```bash
+grep 'replace tailscale.com' /path/to/coder/coder/go.mod
+```
+
+### vishvananda/netlink and tailscale/netlink
+
+`tailscale/netlink` is a fork of `vishvananda/netlink` from 2021. Starting from
+`vishvananda/netlink` v1.3.0, the `XfrmAddress.ToIPNet` method gained an
+additional `family uint16` parameter, which breaks `tailscale/netlink`.
+
+If a transitive dependency (e.g. `containerd/containerd/v2`) pulls in
+`vishvananda/netlink` >= v1.3.0, you will see build errors like:
+
+```
+not enough arguments in call to msg.Sel.Daddr.ToIPNet
+    have (uint8)
+    want (uint8, uint16)
+```
+
+The fix is to add `exclude` directives in `go.mod` for the incompatible
+versions, forcing Go to select v1.2.x:
+
+```
+exclude (
+    github.com/vishvananda/netlink v1.3.0
+    github.com/vishvananda/netlink v1.3.1-0.20250303224720-0e7078ed04c8
+)
+```
+
+You may need to add additional exclude directives if new versions are released.
+
+### moby/go-archive
+
+`docker/docker` (the `+incompatible` module) imports `github.com/moby/go-archive`
+and expects certain symbols (`archive.Uncompressed`, `archive.Compression`) at the
+package root. In `moby/go-archive` v0.2.0, these were moved to a `compression`
+subpackage and the top-level aliases were removed.
+
+If you see errors like:
+
+```
+undefined: archive.Uncompressed
+undefined: archive.Compression
+```
+
+Pin `moby/go-archive` to v0.1.0 in `go.mod`:
+
+```bash
+go mod edit -require 'github.com/moby/go-archive@v0.1.0'
+go mod tidy
+```
+
+### General upgrade workflow
+
+When upgrading `coder/coder/v2` or other major dependencies:
+
+1. Update the dependency version in `go.mod`.
+2. Compare replace directives (especially `tailscale.com`) against the
+   upstream module's `go.mod` and update to match.
+3. Run `go mod tidy`.
+4. Run `go build ./...` and check for compilation errors.
+5. If you see errors from transitive dependencies, check whether version
+   conflicts can be resolved with `exclude` directives or by pinning
+   specific versions with `go mod edit -require`.
+6. Run `make test` to verify everything works end-to-end.