autodetect: set credential.provider after autodetect

After we've detected the host provider from an auto-detection network
probe, set the `credential.provider` setting so we can avoid the
expensive operation in the future.

If we fail to set this then warn the user and ask them to set the
configuration manually.

Author: mjcheetham

docs/autodetect.md

@@ -31,6 +31,11 @@ hostname can be made. Only one HTTP `HEAD` call is made per credential request
 received by Git. To avoid this network call, please [explicitly configure](#explicit-configuration)
 the host provider for your self-hosted instance.
 
+After a successful detection of the host provider, GCM will automatically set
+the [`credential.provider` configuration entry](configuration.md#credentialprovider)
+for that remote to avoid needing to perform this expensive network call in
+future requests.
+
 ### Timeout
 
 You can control how long GCM will wait for a response to the remote network call
@@ -41,7 +46,7 @@ Git configuration setting to the maximum number of milliseconds to wait.
 The default value is 2000 milliseconds (2 seconds). You can prevent the network
 call altogether by setting a zero or negative value, for example -1.
 
-## Explicit configuration
+## Manual configuration
 
 If the auto-detection mechanism fails to select the correct host provider, or
 if the remote probing network call is causing performance issues, you can

src/shared/Core.Tests/HostProviderRegistryTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Net;
 using System.Net.Http;
 using System.Threading.Tasks;
@@ -48,7 +49,8 @@ public async Task HostProviderRegistry_GetProvider_Auto_HasProviders_ReturnsSupp
         {
             var context = new TestCommandContext();
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -66,12 +68,69 @@ public async Task HostProviderRegistry_GetProvider_Auto_HasProviders_ReturnsSupp
             Assert.Same(provider2Mock.Object, result);
         }
 
+        [Fact]
+        public async Task HostProviderRegistry_GetProvider_Auto_HasProviders_SetsProviderGlobalConfig()
+        {
+            var context = new TestCommandContext();
+            var registry = new HostProviderRegistry(context);
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
+
+            string providerId = "myProvider";
+            string configKey = string.Format(CultureInfo.InvariantCulture,
+                "{0}.https://example.com.{1}",
+                Constants.GitConfiguration.Credential.SectionName,
+                Constants.GitConfiguration.Credential.Provider);
+
+            var providerMock = new Mock<IHostProvider>();
+            providerMock.Setup(x => x.Id).Returns(providerId);
+            providerMock.Setup(x => x.IsSupported(It.IsAny<InputArguments>())).Returns(true);
+
+            registry.Register(providerMock.Object, HostProviderPriority.Normal);
+
+            IHostProvider result = await registry.GetProviderAsync(input);
+
+            Assert.Same(providerMock.Object, result);
+            Assert.True(context.Git.Configuration.Global.TryGetValue(configKey, out IList<string> config));
+            Assert.Equal(1, config.Count);
+            Assert.Equal(providerId, config[0]);
+        }
+
+        [Fact]
+        public async Task HostProviderRegistry_GetProvider_Auto_HasProviders_SetsProviderGlobalConfig_HostWithPath()
+        {
+            var context = new TestCommandContext();
+            var registry = new HostProviderRegistry(context);
+            var remote = new Uri("https://example.com/alice/repo.git/");
+            InputArguments input = CreateInputArguments(remote);
+
+            string providerId = "myProvider";
+            string configKey = string.Format(CultureInfo.InvariantCulture,
+                "{0}.https://example.com/alice/repo.git.{1}", // expect any trailing slash to be removed
+                Constants.GitConfiguration.Credential.SectionName,
+                Constants.GitConfiguration.Credential.Provider);
+
+            var providerMock = new Mock<IHostProvider>();
+            providerMock.Setup(x => x.Id).Returns(providerId);
+            providerMock.Setup(x => x.IsSupported(It.IsAny<InputArguments>())).Returns(true);
+
+            registry.Register(providerMock.Object, HostProviderPriority.Normal);
+
+            IHostProvider result = await registry.GetProviderAsync(input);
+
+            Assert.Same(providerMock.Object, result);
+            Assert.True(context.Git.Configuration.Global.TryGetValue(configKey, out IList<string> config));
+            Assert.Equal(1, config.Count);
+            Assert.Equal(providerId, config[0]);
+        }
+
         [Fact]
         public async Task HostProviderRegistry_GetProvider_Auto_MultipleValidProviders_ReturnsFirstRegistered()
         {
             var context = new TestCommandContext();
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -94,7 +153,8 @@ public async Task HostProviderRegistry_GetProvider_Auto_MultipleValidProvidersMu
         {
             var context = new TestCommandContext();
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -152,7 +212,8 @@ public async Task HostProviderRegistry_GetProvider_AutoProviderSpecified_Returns
                 Settings = {ProviderOverride = Constants.ProviderIdAuto}
             };
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -181,7 +242,8 @@ public async Task HostProviderRegistry_GetProvider_UnknownProviderSpecified_Retu
                 Settings = {ProviderOverride = "provider42"}
             };
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -239,7 +301,8 @@ public async Task HostProviderRegistry_GetProvider_AutoLegacyAuthoritySpecified_
                 Settings = {LegacyAuthorityOverride = Constants.AuthorityIdAuto}
             };
             var registry = new HostProviderRegistry(context);
-            var input = new InputArguments(new Dictionary<string, string>());
+            var remote = new Uri("https://example.com");
+            InputArguments input = CreateInputArguments(remote);
 
             var provider1Mock = new Mock<IHostProvider>();
             var provider2Mock = new Mock<IHostProvider>();
@@ -266,13 +329,7 @@ public async Task HostProviderRegistry_GetProvider_Auto_NetworkProbe_ReturnsSupp
             var context = new TestCommandContext();
             var registry = new HostProviderRegistry(context);
             var remoteUri = new Uri("https://provider2.onprem.example.com");
-            var input = new InputArguments(
-                new Dictionary<string, string>
-                {
-                    ["protocol"] = remoteUri.Scheme,
-                    ["host"] = remoteUri.Host
-                }
-            );
+            InputArguments input = CreateInputArguments(remoteUri);
 
             var provider1Mock = new Mock<IHostProvider>();
             provider1Mock.Setup(x => x.IsSupported(It.IsAny<InputArguments>())).Returns(false);
@@ -408,5 +465,21 @@ public async Task HostProviderRegistry_GetProvider_Auto_NetworkProbe_NoNetwork_R
             httpHandler.AssertRequest(HttpMethod.Head, remoteUri, 1);
             Assert.Same(lowProviderMock.Object, result);
         }
+
+        public static InputArguments CreateInputArguments(Uri uri)
+        {
+            var dict = new Dictionary<string, string>
+            {
+                ["protocol"] = uri.Scheme,
+                ["host"] = uri.IsDefaultPort ? uri.Host : $"{uri.Host}:{uri.Port}"
+            };
+
+            if (!string.IsNullOrWhiteSpace(uri.AbsolutePath) && uri.AbsolutePath != "/")
+            {
+                dict["path"] = uri.AbsolutePath.TrimEnd('/');
+            }
+
+            return new InputArguments(dict);
+        }
     }
 }

src/shared/Core/HostProviderRegistry.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.Linq;
 using System.Net.Http;
 using System.Threading.Tasks;
@@ -143,10 +144,15 @@ public async Task<IHostProvider> GetProviderAsync(InputArguments input)
 
             //
             // Auto-detection
+            // Perform auto-detection network probe and remember the result
             //
             _context.Trace.WriteLine("Performing auto-detection of host provider.");
 
             var uri = input.GetRemoteUri();
+            if (uri is null)
+            {
+                throw new Exception("Unable to detect host provider without a remote URL");
+            }
 
             var probeTimeout = TimeSpan.FromMilliseconds(_context.Settings.AutoDetectProviderTimeout);
             _context.Trace.WriteLine($"Auto-detect probe timeout is {probeTimeout.TotalSeconds} ms.");
@@ -209,10 +215,32 @@ async Task<IHostProvider> MatchProviderAsync(HostProviderPriority priority)
             }
 
             // Match providers starting with the highest priority
-            return await MatchProviderAsync(HostProviderPriority.High) ??
-                   await MatchProviderAsync(HostProviderPriority.Normal) ??
-                   await MatchProviderAsync(HostProviderPriority.Low) ??
-                   throw new Exception("No host provider available to service this request.");
+            IHostProvider match = await MatchProviderAsync(HostProviderPriority.High) ??
+                                  await MatchProviderAsync(HostProviderPriority.Normal) ??
+                                  await MatchProviderAsync(HostProviderPriority.Low) ??
+                                  throw new Exception("No host provider available to service this request.");
+
+            // Set the host provider explicitly for future calls
+            IGitConfiguration gitConfig = _context.Git.GetConfiguration();
+            var keyName = string.Format(CultureInfo.InvariantCulture, "{0}.{1}.{2}",
+                Constants.GitConfiguration.Credential.SectionName, uri.ToString().TrimEnd('/'),
+                Constants.GitConfiguration.Credential.Provider);
+
+            try
+            {
+                _context.Trace.WriteLine($"Remembering host provider for '{uri}' as '{match.Id}'...");
+                gitConfig.Set(GitConfigurationLevel.Global, keyName, match.Id);
+            }
+            catch (Exception ex)
+            {
+                _context.Trace.WriteLine("Failed to set host provider!");
+                _context.Trace.WriteException(ex);
+
+                _context.Streams.Error.WriteLine("warning: failed to remember result of host provider detection!");
+                _context.Streams.Error.WriteLine($"warning: try setting this manually: `git config --global {keyName} {match.Id}`");
+            }
+
+            return match;
         }
 
         public void Dispose()