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refactor(merger): build the git command env from the shared composer #612

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Merged
behinddwalls merged 1 commit into from
Aug 19, 2026
+18 −68
Merged

refactor(merger): build the git command env from the shared composer #612

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1 change: 1 addition & 0 deletions runway/extension/merger/git/BUILD.bazel
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@ go_library(
"//api/runway/messagequeue/protopb:go_default_library",
"//platform/base/change/git:go_default_library",
"//platform/base/change/github:go_default_library",
"//platform/git/exec:go_default_library",
"//platform/metrics:go_default_library",
"//runway/extension/merger:go_default_library",
"@com_github_uber_go_tally//:go_default_library",
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85 changes: 17 additions & 68 deletions runway/extension/merger/git/git_merger.go
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,6 @@ import (
"context"
"errors"
"fmt"
"os"
"os/exec"
"path/filepath"
"strings"
Expand All @@ -89,6 +88,7 @@ import (
mergestrategypb "github.com/uber/submitqueue/api/base/mergestrategy/protopb"
runwaymq "github.com/uber/submitqueue/api/runway/messagequeue"
runwaypb "github.com/uber/submitqueue/api/runway/messagequeue/protopb"
gitexec "github.com/uber/submitqueue/platform/git/exec"
coremetrics "github.com/uber/submitqueue/platform/metrics"
"github.com/uber/submitqueue/runway/extension/merger"
)
Expand Down Expand Up @@ -1094,76 +1094,25 @@ func newGitCommand(ctx context.Context, runtime GitRuntime, dir string, args ...

cmd := exec.CommandContext(ctx, runtime.Executable, gitArgs...)
cmd.Dir = dir
cmd.Env = []string{
"HOME=" + filepath.Join(dir, ".submitqueue-git-home"),
"XDG_CONFIG_HOME=" + filepath.Join(dir, ".submitqueue-git-home", "xdg"),
"GIT_CONFIG_NOSYSTEM=1",
"GIT_CONFIG_GLOBAL=" + os.DevNull,
"GIT_ATTR_NOSYSTEM=1",
"GIT_TERMINAL_PROMPT=0",
"GIT_PAGER=cat",
"GIT_EDITOR=:",
"GIT_EXEC_PATH=" + runtime.ExecPath,
"GIT_TEMPLATE_DIR=" + runtime.TemplateDir,
"LC_ALL=C",
"LANG=C",
}
cmd.Env = append(cmd.Env, passthroughEnv(runtime.PassthroughEnv)...)
// HOME and XDG_CONFIG_HOME are isolated to the checkout rather than inherited,
// so the runtime's literals — appended last — override any HOME a deployment
// passed through. The remaining literals pin git's runtime; the scrub set and
// transport variables come from the shared composer.
cmd.Env = gitexec.Env(gitexec.EnvOptions{
Transport: true,
Passthrough: runtime.PassthroughEnv,
Literal: []string{
"HOME=" + filepath.Join(dir, ".submitqueue-git-home"),
"XDG_CONFIG_HOME=" + filepath.Join(dir, ".submitqueue-git-home", "xdg"),
"GIT_EXEC_PATH=" + runtime.ExecPath,
"GIT_TEMPLATE_DIR=" + runtime.TemplateDir,
"LC_ALL=C",
"LANG=C",
},
})
return cmd
}

// authEnvNames are the variables inherited from the parent process when set.
//
// Scrubbing the environment is about denying git ambient *configuration* that
// could change what a merge produces. Reaching the remote is a separate
// concern, and these carry it: an SSH remote authenticates through the agent
// socket, git locates its ssh and credential helpers through PATH, and TLS and
// proxy settings decide whether an HTTPS remote is reachable at all. Dropping
// them does not make the merge more hermetic, it just makes fetch and push
// fail — and at Uber, where a uSSH certificate lives in the agent, it fails as
// an opaque authentication error rather than an obviously missing variable.
//
// None of these can influence merge semantics, which is what keeps them
// compatible with the scrubbing above.
var authEnvNames = []string{
"SSH_AUTH_SOCK",
"SSH_AGENT_PID",
"PATH",
"GIT_SSH",
"GIT_SSH_COMMAND",
"GIT_SSH_VARIANT",
"GIT_SSL_CAINFO",
"GIT_SSL_CAPATH",
"SSL_CERT_DIR",
"SSL_CERT_FILE",
"HTTP_PROXY", "HTTPS_PROXY", "NO_PROXY",
"http_proxy", "https_proxy", "no_proxy",
}

// passthroughEnv returns "NAME=value" entries for the auth and transport
// variables that are actually set, plus any extra names the deployment asked
// for. An unset variable is omitted rather than exported empty, which for
// SSH_AUTH_SOCK is the difference between "use the agent" and "there is no
// agent".
func passthroughEnv(extra []string) []string {
names := make([]string, 0, len(authEnvNames)+len(extra))
names = append(names, authEnvNames...)
names = append(names, extra...)

seen := make(map[string]bool, len(names))
env := make([]string, 0, len(names))
for _, name := range names {
if name == "" || seen[name] {
continue
}
seen[name] = true
if v, ok := os.LookupEnv(name); ok {
env = append(env, name+"="+v)
}
}
return env
}

// isConcreteStrategy reports whether s names a concrete integration strategy
// (i.e. not DEFAULT and not an unknown value).
func isConcreteStrategy(s mergestrategypb.Strategy) bool {
Expand Down
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