feat: explain failed requests and exit silently on interrupt

Failures of tea's own API requests now name what was missing or refused
instead of "resource or API endpoint unavailable":

  issue #999 not found in alice/project
  repository alice/nope not found on http://localhost:3001 (or you don't have access)
  issues are disabled for bob/project
  #1 in alice/project is an issue, not a pull request; view it with: tea issue view 1
  alice/old-stuff is archived (read-only); unarchive it with: tea repo edit ...

A 404 on a repository endpoint looks the repository up once to tell a missing
or hidden repository from a disabled feature, an empty repository or an issue
number given to a pull request command. Refusals get their next step, a
rejected GITEA_TOKEN and unreachable servers are named, and timeoutError words
an expired --timeout. Errors a command already wrapped with its own context,
and raw tea api responses, keep their wording.

Ctrl-C and SIGTERM exit with 130 without printing an error, and a declined
confirmation prints "Canceled." with exit code 3.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/errors_test.go

@@ -0,0 +1,114 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package app
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"gitea.dev/tea/internal/clierr"
+	"github.com/stretchr/testify/require"
+)
+
+// fakeGitea answers the requests in responses, keyed by "METHOD path", with a status and body,
+// and every other request with Gitea's bare 404.
+func fakeGitea(t *testing.T, responses map[string][2]string) *httptest.Server {
+	t.Helper()
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		response, ok := responses[r.Method+" "+r.URL.Path]
+		if !ok {
+			response = [2]string{"404", `{"message":"not found"}`}
+		}
+		var status int
+		_, _ = fmt.Sscan(response[0], &status)
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(status)
+		_, _ = w.Write([]byte(response[1]))
+	}))
+	t.Cleanup(server.Close)
+	return server
+}
+
+func TestExplainNamesResourcesAndTellsWhyRepositoriesFail(t *testing.T) {
+	server := fakeGitea(t, map[string][2]string{
+		"GET /api/v1/user":                                {"200", `{"login":"alice"}`},
+		"GET /api/v1/repos/alice/project":                 {"200", `{"full_name":"alice/project","has_issues":true,"has_pull_requests":true}`},
+		"GET /api/v1/repos/alice/project/issues/1":        {"200", `{"number":1,"pull_request":null}`},
+		"GET /api/v1/repos/bob/project":                   {"200", `{"full_name":"bob/project","has_issues":false,"has_pull_requests":true}`},
+		"GET /api/v1/repos/alice/empty":                   {"200", `{"full_name":"alice/empty","empty":true,"has_issues":true,"has_pull_requests":true}`},
+		"GET /api/v1/repos/alice/old":                     {"200", `{"full_name":"alice/old","archived":true,"has_issues":true}`},
+		"POST /api/v1/repos/alice/old/issues":             {"423", `{"message":"repo is archived"}`},
+		"POST /api/v1/repos/alice/project/pulls":          {"409", `{"message":"pull request already exists for these targets [id: 16, issue_id: 3, head_repo_id: 1, base_repo_id: 1, head_branch: feat, base_branch: main]"}`},
+		"GET /api/v1/repos/alice/project/pulls/main/feat": {"200", `{"number":3,"html_url":"https://example.org/alice/project/pulls/3"}`},
+		"GET /api/v1/repos/alice/project/pulls/3":         {"200", `{"number":3,"state":"open","draft":true,"head":{"sha":"abc"}}`},
+		"POST /api/v1/repos/alice/project/pulls/3/merge":  {"405", `{"message":"Work in progress PRs cannot be merged"}`},
+	})
+	for _, tc := range []struct {
+		name string
+		args []string
+		want string
+	}{
+		{"missing issue", []string{"issue", "view", "999", "-R", "alice/project"}, "issue #999 not found in alice/project"},
+		{"missing repository", []string{"issue", "list", "-R", "alice/nope"}, "repository alice/nope not found on " + server.URL + " (or you don't have access)"},
+		{"disabled issues", []string{"issue", "list", "-R", "bob/project"}, "issues are disabled for bob/project"},
+		{"issue as pull request", []string{"pr", "view", "1", "-R", "alice/project"}, "#1 in alice/project is an issue, not a pull request; view it with: tea issue view 1"},
+		{"missing pull request", []string{"pr", "view", "999", "-R", "alice/project"}, "pull request #999 not found in alice/project"},
+		{"empty repository", []string{"pr", "list", "-R", "alice/empty"}, "alice/empty is empty; it has no pull requests"},
+		{"archived repository", []string{"issue", "create", "-R", "alice/old", "--title", "x", "--body", "y"}, "alice/old is archived (read-only); unarchive it with: tea repo edit alice/old --archived=false"},
+		{"existing pull request", []string{"pr", "create", "-R", "alice/project", "--head", "feat", "--base", "main", "--title", "x", "--body", "y"}, "pull request for feat into main already exists in alice/project; see https://example.org/alice/project/pulls/3"},
+		{"context added by the command", []string{"pr", "merge", "3", "-R", "alice/project", "--yes"}, "pull request #3 is a draft; mark it ready for review first: Gitea API returned HTTP 405 for POST /api/v1/repos/alice/project/pulls/3/merge: Work in progress PRs cannot be merged"},
+		{"raw api response", []string{"api", "users/nobody"}, "not found (HTTP 404 GET /api/v1/users/nobody)"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			deps, _, _ := serverDeps(t, server.URL)
+			err := Execute(context.Background(), deps, append(tc.args, "--no-input"))
+			require.Error(t, err)
+			explained := Explain(context.Background(), deps, err)
+			require.EqualError(t, explained, tc.want)
+			require.Equal(t, clierr.ExitCode(err), clierr.ExitCode(explained))
+		})
+	}
+}
+
+func TestExplainWordsCredentialAndConnectionFailures(t *testing.T) {
+	rejecting := fakeGitea(t, map[string][2]string{"GET /api/v1/user": {"401", `{"message":"token is invalid"}`}})
+	deps, _, _ := serverDeps(t, rejecting.URL)
+	err := Execute(context.Background(), deps, []string{"issue", "list", "-R", "alice/project"})
+	explained := Explain(context.Background(), deps, err)
+	require.EqualError(t, explained, "GITEA_TOKEN was rejected by "+rejecting.URL+"; fix or unset GITEA_TOKEN")
+	require.Equal(t, clierr.Authentication, clierr.ExitCode(explained))
+
+	closed := httptest.NewServer(http.NotFoundHandler())
+	closed.Close()
+	deps, _, _ = serverDeps(t, closed.URL)
+	err = Execute(context.Background(), deps, []string{"issue", "list", "-R", "alice/project"})
+	require.EqualError(t, Explain(context.Background(), deps, err), "cannot reach "+closed.URL+" (connection refused); check --host or your network")
+}
+
+func TestTimeoutErrorsNameTheWaitAndKeepTheExitCode(t *testing.T) {
+	err := fmt.Errorf("watch: %w", context.DeadlineExceeded)
+	for _, tc := range []struct {
+		d    time.Duration
+		want string
+	}{
+		{4 * time.Second, "timed out after 4s waiting for run 34"},
+		{time.Hour, "timed out after 1h waiting for run 34"},
+		{90 * time.Minute, "timed out after 1h30m waiting for run 34"},
+		{2 * time.Minute, "timed out after 2m waiting for run 34"},
+	} {
+		timeout := timeoutError(err, tc.d, "waiting for run %d", 34)
+		require.EqualError(t, timeout, tc.want)
+		require.ErrorIs(t, timeout, context.DeadlineExceeded)
+		require.Equal(t, clierr.ExitCode(err), clierr.ExitCode(timeout))
+		require.Equal(t, timeout, Explain(context.Background(), Dependencies{}, timeout), "explained errors are kept")
+	}
+	other := errors.New("boom")
+	require.Equal(t, other, timeoutError(other, time.Second, "waiting"))
+	require.EqualError(t, Explain(context.Background(), Dependencies{}, err), "timed out before the operation finished")
+}