WatchConfig.UpsertEntry silently deletes existing contexts when re-upserting a watched file #610

Describe the bug

When a file is being watched across multiple contexts (e.g. ["dev", "staging"]), re-running microcks import --watch <file> on an existing context—or calling WatchConfig.UpsertEntry with a context already present—silently deletes all other contexts associated with that file from .config/microcks/watch.

In pkg/config/localconfig.go:

func (w *WatchConfig) UpsertEntry(entry WatchEntry) {
    for i, e := range w.Entries {
        if e.FilePath == entry.FilePath {
            contexts := w.Entries[i].Context
            if !slices.Contains(contexts, entry.Context[0]) {
                entry.Context = append(entry.Context, contexts...)
            }
            w.Entries[i] = entry
            return
        }
    }
    w.Entries = append(w.Entries, entry)
}

If entry.Context[0] is already in contexts, the if !slices.Contains(...) check evaluates to false and does nothing. Because entry.Context only contains the single context from the current invocation, w.Entries[i] = entry replaces the existing context slice with only entry.Context, wiping out all other contexts.

Additionally:

• If entry.Context is empty, accessing entry.Context[0] unconditionally panics with runtime error: index out of range [0] with length 0.
• If entry.Context contains multiple items, only index 0 is ever evaluated.

Expected behavior

WatchConfig.UpsertEntry should preserve all existing contexts for a file while adding any new context without duplicates. Re-importing or updating a watched file from one context must not delete other contexts that are monitoring the same file.

Actual behavior

When re-upserting a file with an already existing context, all other contexts previously attached to the entry are discarded, leaving only the single re-upserted context in the watch configuration.

How to Reproduce?

Reproducer

package main

import (
    "fmt"
    "github.com/microcks/microcks-cli/pkg/config"
)

func main() {
    cfg := config.WatchConfig{
        Entries: []config.WatchEntry{
            {FilePath: "api.yaml", Context: []string{"dev"}},
        },
    }

    // 1. Add "staging" -> Entry has ["staging", "dev"]
    cfg.UpsertEntry(config.WatchEntry{FilePath: "api.yaml", Context: []string{"staging"}})
    fmt.Printf("After adding staging: %v\n", cfg.Entries[0].Context)

    // 2. Re-import / re-upsert from "staging"
    cfg.UpsertEntry(config.WatchEntry{FilePath: "api.yaml", Context: []string{"staging"}, MainArtifact: true})
    fmt.Printf("After re-upserting staging: %v\n", cfg.Entries[0].Context)

    // Output: [staging] --> "dev" context was deleted!
}

Steps to Reproduce via CLI

1. Register a file in watch mode across two contexts (dev and staging).
2. Run microcks import --watch <file> again while on the staging context.
3. Check the watch configuration file: <file> now only lists staging, and dev has been deleted.

Microcks version or git rev

master

Install method (docker-compose, helm chart, operator, docker-desktop extension,...)

No response

Additional information

I would be happy to submit a PR with unit test coverage if the team agrees!