feat(git-remote-entire): honour GIT_HTTP_USER_AGENT for the HTTP User-Agent

[toothbrush]

https://entire.io/gh/entireio/cli/trails/1519

Why

Anyone running git-remote-entire from automation (CI runners, Buildkite plugins, scripts) wants their traffic distinguishable in server access logs. Git already has the knob for this; the helper ignored it and always sent git-remote-entire/<version>.

What

git-remote-entire now honours git's own GIT_HTTP_USER_AGENT for the HTTP User-Agent header, matching git-config(1), http.userAgent:

The HTTP USER_AGENT string presented to an HTTP server. The default value represents the version of the Git client such as git/1.7.1. This option allows you to override this value to a more common value such as Mozilla/4.0. [...] Can be overridden by the GIT_HTTP_USER_AGENT environment variable.

Behaviour, verified against git 2.55.0 with a header-dumping server:

• unset: helper default git-remote-entire/<version> (git: git/2.55.0)
• set: value sent verbatim, any shape (git: same)
• set but empty: no User-Agent header at all (git: same; curl drops the header for an empty CURLOPT_USERAGENT)

transport.Config.UserAgent == "" now sends no header instead of Go's Go-http-client/1.1, so the auth client and the git-transport client behave the same way.

A value net/http would refuse (CR, LF, NUL) fails up front with fatal: GIT_HTTP_USER_AGENT holds an invalid header character (exit 128) instead of every request dying on an anonymous header error.

The helper now strips ref-in-want from the v2 fetch= capability it relays to native git. It proxies each fetch POST to a replica, so a server-side want-ref lookup could race the ls-refs answer git already saw; the data plane hid the feature only for the default git-remote-entire/ User-Agent, which this override can change. A fetch line left with no feature becomes the bare key fetch, which gitprotocol-v2(5) allows (capability = PKT-LINE(key[=value] LF)).

Unchanged and deliberate:

• The pkt-line agent= capability still carries the helper's own identifier. It is a single whitespace-free protocol token, so it is never user-controlled.
• Nothing Entire-specific was added: no new env var, flag, or config key. Only git's own name.

Not done: the http.userAgent config key is not read. The helper never shells out to git config, and git forwards only -c overrides (not .gitconfig) to helpers via GIT_CONFIG_PARAMETERS, so supporting it would need a new subprocess for a partial result. Git documents the env var as the override that wins anyway.

Verification

• go test ./cmd/git-remote-entire/... ./internal/remotehelper/... and go vet: pass
• golangci-lint run on both packages: 0 issues; gofmt -l -s clean
• New TestResolveHTTPUserAgent (table, parallel, env injected) and TestHTTPUserAgent_ReachesServer (builds the auth client as run() does against an httptest.Server and asserts the received header for default / override / empty)
• TestProxy_EmptyUserAgentSendsNoHeader replaces the old "falls back to Go default" expectation
• Git behaviour pinned empirically on git 2.55.0: GIT_HTTP_USER_AGENT="" sends no header; env beats -c http.userAgent; -c reaches a remote helper only as GIT_CONFIG_PARAMETERS='http.userAgent'='…'

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The implementation consistently covers both HTTP paths and includes focused regression tests.

0 open findings

What changed in this PR

Aligns git-remote-entire HTTP identification with Git’s GIT_HTTP_USER_AGENT behavior.

Changes:

• Resolves HTTP user-agent overrides while preserving the fixed protocol agent.
• Suppresses Go’s default header when the override is empty.
• Adds documentation and coverage for default, overridden, and empty values.

File	Description
README.md	Documents the supported environment variable.
cmd/​git-remote-entire/​main.go	Resolves and applies the HTTP user-agent.
cmd/​git-remote-entire/​main_test.go	Tests resolution and auth-path requests.
internal/​remotehelper/​transport/​proxy.go	Always wraps transports to support empty-header suppression.
internal/​remotehelper/​transport/​proxy_test.go	Verifies empty values omit the header.

🧠 Review effort: Balanced

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