Handle differences in user environments while executing hooks (#696)

* Handle user shell not being bash

* Better handling for differences evaluating PATH in user shells

* Follow Git behavior and fallback to using sh to execute hooks

Author: zwaldowski

Diff for: GitUpKit/Core/GCPrivate.h

@@ -138,6 +138,7 @@ extern int git_submodule_foreach_block(git_repository* repo, int (^block)(git_su
 @property(nonatomic) NSTimeInterval executionTimeOut;  // Default is 0.0 i.e. no timeout
 @property(nonatomic, copy) NSDictionary* additionalEnvironment;
 @property(nonatomic, copy) NSString* currentDirectoryPath;
+@property(nonatomic) BOOL fallBackToDefaultInterpreter;
 - (instancetype)initWithExecutablePath:(NSString*)path;
 - (BOOL)runWithArguments:(NSArray*)arguments stdin:(NSData*)stdin stdout:(NSData**)stdout stderr:(NSData**)stderr exitStatus:(int*)exitStatus error:(NSError**)error;  // Returns NO if "exitStatus" is NULL and executable exits with a non-zero status
 @end

Diff for: GitUpKit/Core/GCPrivate.m

@@ -67,20 +67,21 @@ - (void)_fileHandleDataAvailable:(NSNotification*)notification {
   }
 }
 
-- (BOOL)runWithArguments:(NSArray*)arguments stdin:(NSData*)stdin stdout:(NSData**)stdout stderr:(NSData**)stderr exitStatus:(int*)exitStatus error:(NSError**)error {
+- (BOOL)_runWithDefaultInterpreter:(BOOL)useSH arguments:(NSArray*)arguments stdin:(NSData*)stdin stdout:(NSData**)stdout stderr:(NSData**)stderr exitStatus:(int*)exitStatus error:(NSError**)error {
   BOOL success = NO;
   NSPipe* inPipe = nil;
   NSPipe* outPipe = nil;
   NSPipe* errorPipe = nil;
   NSTimer* timer = nil;
 
   NSTask* task = [[NSTask alloc] init];
-  task.launchPath = _executablePath;
+  task.launchPath = useSH ? @"/bin/sh" : _executablePath;
   NSMutableDictionary* environment = [[NSMutableDictionary alloc] initWithDictionary:[[NSProcessInfo processInfo] environment]];
   [environment addEntriesFromDictionary:_additionalEnvironment];
   task.environment = environment;
   task.currentDirectoryPath = _currentDirectoryPath ? _currentDirectoryPath : [[NSFileManager defaultManager] currentDirectoryPath];
-  task.arguments = arguments ? arguments : @[];
+  NSArray* interpreterArguments = useSH ? @[ _executablePath ] : @[];
+  task.arguments = [interpreterArguments arrayByAddingObjectsFromArray:arguments];
 
   if (stdin) {
     inPipe = [[NSPipe alloc] init];
@@ -170,6 +171,11 @@ - (BOOL)runWithArguments:(NSArray*)arguments stdin:(NSData*)stdin stdout:(NSData
   return success;
 }
 
+
+- (BOOL)runWithArguments:(NSArray*)arguments stdin:(NSData*)stdin stdout:(NSData**)stdout stderr:(NSData**)stderr exitStatus:(int*)exitStatus error:(NSError**)error {
+  return [self _runWithDefaultInterpreter:NO arguments:arguments stdin:stdin stdout:stdout stderr:stderr exitStatus:exitStatus error:error] || (self.fallBackToDefaultInterpreter && [self _runWithDefaultInterpreter:YES arguments:arguments stdin:stdin stdout:stdout stderr:stderr exitStatus:exitStatus error:error]);
+}
+
 @end
 
 #endif

Diff for: GitUpKit/Core/GCRepository.m

@@ -310,24 +310,32 @@ - (NSString*)pathForHookWithName:(NSString*)name {
   return [[NSFileManager defaultManager] isExecutableFileAtPath:path] ? path : nil;
 }
 
+- (NSString*)getPATHUsingShell:(NSString*)shell error:(NSError**)error {
+  GCTask* task = [[GCTask alloc] initWithExecutablePath:shell];
+  NSData* data;
+  // `-l` is not supported with `-c` in all shells (tcsh), so try without.
+  // Some shells use quoting of $PATH to trigger POSIX compatibility behavior (fish).
+  // Not all shells support `-n` on `echo`.
+  if (![task runWithArguments:@[ @"-l", @"-c", @"echo \"$PATH\"" ] stdin:NULL stdout:&data stderr:NULL exitStatus:NULL error:error] && ![task runWithArguments:@[ @"-c", @"echo \"$PATH\"" ] stdin:NULL stdout:&data stderr:NULL exitStatus:NULL error:error]) {
+    return nil;
+  }
+  return [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] stringByTrimmingCharactersInSet:[NSCharacterSet newlineCharacterSet]];
+}
+
 - (BOOL)runHookWithName:(NSString*)name arguments:(NSArray*)arguments standardInput:(NSString*)standardInput error:(NSError**)error {
   NSString* path = [self pathForHookWithName:name];
   if (path) {
     static NSString* cachedPATH = nil;
     if (cachedPATH == nil) {
-      GCTask* task = [[GCTask alloc] initWithExecutablePath:@"/bin/bash"];  // TODO: Handle user shell not being bash
-      NSData* data;
-      if (![task runWithArguments:@[ @"-l", @"-c", @"echo -n $PATH" ] stdin:NULL stdout:&data stderr:NULL exitStatus:NULL error:error]) {
-        return NO;
-      }
-      cachedPATH = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
+      cachedPATH = [self getPATHUsingShell:NSProcessInfo.processInfo.environment[@"SHELL"] error:error] ?: [self getPATHUsingShell:@"/bin/sh" error:error];
       XLOG_DEBUG_CHECK(cachedPATH);
     }
 
     CFAbsoluteTime time = CFAbsoluteTimeGetCurrent();
     GCTask* task = [[GCTask alloc] initWithExecutablePath:path];
     task.currentDirectoryPath = self.workingDirectoryPath;  // TODO: Is this the right working directory?
     task.additionalEnvironment = @{@"PATH" : cachedPATH};
+    task.fallBackToDefaultInterpreter = YES;
     int status;
     NSData* stdoutData;
     NSData* stderrData;